USA | A Nice Algebra Problem | Math Olympiad
16:04
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@19shg67
@19shg67 14 минут бұрын
Since one equation with two unknowns is given, the considered task has infinitely many solutions. Therefore, this task makes sense only if it needs to be solved in integer numbers. So, it is assumed that x and y are integer numbers. Then the approach you have described (i.e. using the notations a=x^(y/2), b=y^(1/2), transforming the original problem into the form (a-b)*(a+b)={1*77; 7*11}) is invalid, since b=y^(1/2) may not be an integer. P.S. Nevertheless, the equation x^y-y=77 can be solved in integer numbers, but not by your false approach, and by a completely different approach! This equation has a finite number of integer solutions! Best wishes, Sharif E. Guseynov Riga, Latvia
@quynhnguyen3873
@quynhnguyen3873 53 минут бұрын
THẦY Ở COLOMBIA HAY GERMAN?
@ConradoPeter-hl5ij
@ConradoPeter-hl5ij 5 сағат бұрын
(we want to find a p*q=a²+2ab+b; with p and q ∈ N*) So, we will star isolating b and a in the equation to find a divisible term after: For every b and a, not necessarly in Z: a²+2ab+b=44 a²+b(2a+1)=44 2a²+a+b(2a+1)=44+a²+a a(2a+1)+b(2a+1)=44+a²+a (a+b)(2a+1)=44+a²+a a+b= [a²+a+44]/(2a+1) ● b = {[a²+a+44]/(2a+1)}-a; with 2a+1≠0 But, remember b ∈ N*, then: make it: Q(a)=a²+a+44 and q(a)=2a+1 then, [a²+a+44]/(2a+1)=[Q(a)]/[q(a)]=p(a) and p(a)=n, n ∈ N*. /////////////////////////////////////////////////// finding the p(a) and r(a): Q(a) = a² + a + 44 | q(a) =(2a+1) -a² - a/2 ||p(a)=(a/2)+(1/4) -----------‐ 0 + a/2 + 44 - a/2 - 1/4 ------------------- 0 + 175/4 = r(a) ///////////////////////////////////////////////// Constructing p*q into the original equation: So, Q(a)=q(a)*p(a) + r(a) ● a²+a+44=(2a+1)*[(a/2)+(1/4)] +(175/4) retake the original equation: a²+2ab+b=44 a²+b(2a+1)=44 2a²+a+b(2a+1)=44+a²+a a(2a+1)+b(2a+1)=44+a²+a (a+b)(2a+1)=44+a²+a; but remember Q(a)=44+a²+a then, (a+b)(2a+1)=(2a+1)[(a/2)+(1/4)]+(175/4) make 4 times the equation: (4a+4b)(2a+1)=(2a+1)[2a+1]+175 (4a+4b)(2a+1)=(2a+1)²+175 (4a+b)(2a+1) - (2a+1)² =175 (2a+1)[(4a+4b)-(2a+1)]=175 (2a+1)[4a-2a+4b-1]=175 (2a+1)(2a+4b+1)=175 Where are the p and q? It is here the term p=(2a+1) and it the term q=[(2a+1)+4b]. ■(2a+1)[(2a+1)+4b]=175; n=2a+1 better make like this way: ■n(n+4b)=175 Now, we can thing the possibilites: n×(n+4b)=5²×7; with ■D(175)={1;5;7;25;35;175} And ■ n ⊂ D(175) (I) then, n ⊂ {1;5;7;25;35;175} ////////////////////////////////////////////////// Considering the domain of the question: remember that n=2a+1 and consider a ∈ N* because the question already said it. And, remember b ∈ N. And think about a domain of a and b. So, retake a²+2ab+b=44 you can see that each term of the equation cannot be bigger than 44. Then, a²<44; 2ab<44; b<44 taking a²<44 and a ∈ N* then, 0<a<7 but a ∈ N* Therefore, ■ 6≥a≥1 retake n=2a+1 and take 0<a<7. then, ■13≥n≥3. (II) /////////////////////////////////////////////// take (I) and (II): n=5 or n=7 therefore, a=2 or a=3 n×(n+4b)=[D(175)]×[D'(175)] input a={2;3} into equation: a²+2ab+b=44 a=2 2²+2*2*b+b=44 4+4b+b=44 5b=41 b=41/5; but b belongs to N* so, a=2 is not a solution. a=3 3²+2*3*b+b=44 9+6b+b=44 7b=35 b=5 Therefore, ■ a=3 and b=5 is the solution. ------------‐------- / / -----‐------------
@ConradoPeter-hl5ij
@ConradoPeter-hl5ij 8 сағат бұрын
a²+2ab+b=44 a, b ∈ N Then, a² ∈ N, ab ∈ N, (a-b) ∈ Z and (a+b) ∈ N. then, a²<44, 2ab<44, b<44 so, ■a²<44 => a<√44<7 => a<7 then 0<a<7 and a ∈ N ● 6 ≥ a ≥ 1with a ∈ N ■2ab<44 => ab<22 ■b=44-a²-2ab if a=1 (the smalest a possible) then, b=44-1-2b 3b=43 b=43/3≈ 7 (the biggest b); but b ∈ N, then 7≥ b>0 if a=6 (biggest) then, b=44-36-6b 7b=8 b≈1 (smalest) then, ● 7 ≥ b ≥ 1 with b ∈ N ■ab ---> 7*1=7. (smallest ab) 6*2=12 5*3=15 4*4=16 (biggest ab) then, 14 < 2ab < 32 So, a²+2ab+b=44 a²+b=44-2ab 44-14 > a²+b > 44-32 30 > a²+b > 12 then, 30 - b > a² > 12 - b 30 -1 > a² > 12 - 7 29 > a² > 5 36 > 29 > a² > 5. > 4 6² > a² > 2² 6 > a > 2 with a ∈ N then, 5 ≥ a. ≥ 3 input a={3;4;5} in the equation: a²+2ab+b=44 when, a=3 3²+2*3b+b=44 9+6b+b=44 7b=35 => b=5 so, a=3 and b=5 is a solution a=4 4²+2*4b+b=44 16+8b+b=44 16+9b=44 9b=28 b≈7 is not a solution a=5 5²+2*5b+b=44 25+10b+b=44 25+11b=44 11b=19 is not a solution. Therefore, a=3 and b=5 is the anwser.
@edwardwang7929
@edwardwang7929 11 сағат бұрын
Once getting (m+1)^4 - (m-1)^4 = 80,unfolding left side and merging them. 2* (4m^3 + 4m) = 80,then m^3 + m = 10. Guessing m = 2 is one of solutions....
@lollol-tt3fx
@lollol-tt3fx 14 сағат бұрын
WHAT HE FUCK THIS NIS NOT MATH OLYMPIAD LEVEL WHAT IN THE ACTUAL FUCK ARE YOU ON ABOUT THIS IS SO FUCKING DUMB, STOP MAKING HTESE SHITTY CLICKBAITS
@souzasilva5471
@souzasilva5471 14 сағат бұрын
Se tivesse feito 6^x = 3^x *2^x , e a = 3^x; b=2^x, ficaria bem mais simples. Quadrar e dividir por ab. Chegaria em a/b + b/a - 3 = 0, Fazendo a/b = k e ... ( If I had done 6^x = 3^x *2^x , and a= 3^x; b =2^x, it would be much simpler. Square and divide by ab. It would arrive at a/b + b/a - 3 = 0, making a/b = k and...).
@SALogics
@SALogics 14 сағат бұрын
Truque muito bom! ❤
@quynhnguyen3873
@quynhnguyen3873 14 сағат бұрын
Ngủ sớm. Mọi ý tưởng cạn kiệt
@gelbkehlchen
@gelbkehlchen 14 сағат бұрын
Solution: 4^x-8*x = 0 = 4^2-8*2 |The same operations are done on the left side of the equation with x as on the right side of the equation with 2, therefore x = 2. When you use the complicated Lambert function, you make also a comparisation between the left side of the equation with the right side of the equation. And you can save yourself this complicated comparison if you make this comparison right away.
@SALogics
@SALogics 14 сағат бұрын
Very nice trick! ❤
@quynhnguyen3873
@quynhnguyen3873 14 сағат бұрын
Đặt U = . V= -. (U+V)^3 =? (U = a^1/2 .V =b^1/2)
@quynhnguyen3873
@quynhnguyen3873 16 сағат бұрын
KHÔNG ĐỦ KIÊN NHẪN. NHỜ THẦY GIÚP
@quynhnguyen3873
@quynhnguyen3873 16 сағат бұрын
XEM VIET CÓ OK KHÔNG THẦY.
@SALogics
@SALogics 16 сағат бұрын
vâng tại sao không
@quynhnguyen3873
@quynhnguyen3873 16 сағат бұрын
a^2_b^2_a.b=0.
@nasrullahhusnan2289
@nasrullahhusnan2289 17 сағат бұрын
(27^x)+x=0 --> 27^x=-x Raise to 1/x and noting that 27=3³: 3³=(-x)^(1/x) =(1/t)^(-t) by letting t=-1/x =[(1/t)^(-1)]^t =t^t --> t=3 -1/x=3 --> x=-⅓
@SALogics
@SALogics 16 сағат бұрын
Very nice trick! ❤
@quynhnguyen3873
@quynhnguyen3873 17 сағат бұрын
Hằng Đẳng thức hả thầy.
@eduardionovich4425
@eduardionovich4425 17 сағат бұрын
Решил устно. Конечно,знал метод.
@SALogics
@SALogics 16 сағат бұрын
Да, ❤
@RobotKiwiTheFailureKid
@RobotKiwiTheFailureKid 18 сағат бұрын
x=3
@SALogics
@SALogics 16 сағат бұрын
Yes, you are right! ❤
@ConradoPeter-hl5ij
@ConradoPeter-hl5ij 19 сағат бұрын
(x-1)½+(x+2)½=3; make it: u=(x-1)½ and v=(x+2)½ then, u+v=3 (u+v)(u-v)=3(u-v) u²-v²=3(u-v); but u²=(x-1) and v²=x+2 then, (x-1)-(x+2)= 3(u-v) -3=3(u-v) u-v=-1 make the sistem: u+v=3 u-v=-1 then, 2u=2 therefore, u=1 and v=2 But u=(x-1)½ and v=(x+2)½ then, (x-1)½=1 and (x+2)½=2 therefore, x-1=1 => x=2 and x+2=4 =>x=2 therefore, x=2 is a solution. -------‐-------‐------- / / -------‐--------‐‐‐-- simplify one term way: (x-1)½+(x+2)½=3; u=x+2 =>x-1=u-3 (u-3)½+u½=3 (u-3)½=3-u½ (u-3)½=(-1)[(u½)-3] [(u-3)½]²={(-1)[(u½)-3]}² u-3=(-1)²[(u½)-3]² u-3=[(u½)-3]² u-3=(u½)²-2*(u½)*3+3² u-3=u-6(u½)+9 6(u½)=12 u½=2 u=4 but u=x+2; then 4=x+2. therefore x=2 ---------------------- / / --------------------- cheating way: (knowing √1=1) (x-1)½+(x+2)½=3 when x-1=1, then (x-1)½=1 because √1=1. So, 1+√(2+2)=3 1+√4=3 1+2=3 true. therefore x=2 is a solution. ----‐-------------- / / --------------------- algebrical way: (x-1)½+(x+2)½=3; make it: a=(x-1)½ and b=(x+2)½ then a+b=3 b = 3-a b(3+a) = (3-a)(3+a) 3b+ab=3²-a²; but 3=a+b (a+b)b+ab=9-a² ab+b²+ab=9-a² 2ab=9-(a²+b²) 2√(x-1)√(x+2)=9-[(x-1)+(x+2)] 2√[(x-1)(x+2)]=9-[2x+1] 2√[x²+(-1+2)x+(-1)(2)]=9-2x-1 2√[x²+x-2]=8-2x 2(x²+x-2)½=2(4-x) (x²+x-2)½=(4-x); make it: c=(x²+x-2)½ and b=(4-x) c=d c*d=d*d cd=d², but c=d; then cd=c² therefore, c²=d² [(x²+x-2)½]²=(4-x)² x²+x-2=(4²-2*4*x+x²) x²+x-2=(16-8x+x²) x²+(x-2)=x²+(16-8x) (x-2)=(16-8x) (x-2)=8(2-x) (x-2)=8(-1)(x-2) (1)(x-2)=(-8)(x-2); z=x-2 [1)*z=(-8)*z is true only if: z=0 then, x-2=0 x=2 is a solution.
@SALogics
@SALogics 16 сағат бұрын
Very nice trick! I really appreciate that ❤
@SidneiMV
@SidneiMV 20 сағат бұрын
√[6 - √(6 + x)] = x x ≥ 0 √(6 + x) = u √(6 - u) = x 6 + x = u² 6 - u = x² u² - x² = u + x (u + x)(u - x) - (u + x) = 0 (u + x)(u - x - 1) = 0 u = - x ∨ u = x + 1 u = -x => 6 + x = x² x² - x - 6 = 0 (x - 3)(x + 2) = 0 x = 3 ∨ x = -2 [ both are invalid ] u = x + 1 => 6 - (x + 1) = x² x² + x - 5 = 0 *x = (-1 + √21)/2*
@SALogics
@SALogics 16 сағат бұрын
Very nice trick! ❤
@philomenaonumah5949
@philomenaonumah5949 20 сағат бұрын
ab equals 40, so m×m+1=a, and 2m=b
@SALogics
@SALogics 16 сағат бұрын
Very nice trick! ❤
@Arshadee
@Arshadee Күн бұрын
You videos are Brilliant!!! you explain these solutions so well thank you 🙂
@SALogics
@SALogics 16 сағат бұрын
You're very welcome! ❤
@-basicmaths862
@-basicmaths862 Күн бұрын
Answer=25
@SALogics
@SALogics 16 сағат бұрын
Yes, 25 and 1/25
@subratabiswas2502
@subratabiswas2502 Күн бұрын
4ab=(a+b)^2-(a-b)^2 formula should have been applied without going into so much complexity
@SALogics
@SALogics 16 сағат бұрын
Very nice trick! ❤
@adamnyback
@adamnyback Күн бұрын
You forgot to explain the reasoning behind the various steps, in particular the first one.
@SALogics
@SALogics 16 сағат бұрын
I have tried my best to explain everything! ❤
@gasior529
@gasior529 Күн бұрын
3:57 "it is obvious that y=3" NOOO! It is obvious that y=3 IS one of the solutions, but why it is the one and only? It is not obvious! I can say more, if you replace 27 with 0.99 there will be 2 solutions. You HAVE TO JUSTIFY that there is only one solution in this case.
@SALogics
@SALogics 16 сағат бұрын
Is there another solution please share? ❤
@walktowardssunshine4246
@walktowardssunshine4246 Күн бұрын
You make things very lengthy at time. When you found (m^2+1)(2m) =20. Its clear that (2^2+1).2.2 = 5.4 = 20. Thus m = 2.
@SALogics
@SALogics 16 сағат бұрын
Very nice trick! ❤
@quynhnguyen3873
@quynhnguyen3873 15 сағат бұрын
ĐẶT ẨN PHỤ ĐỂ ĐƠN GIẢN HÓA.
@quynhnguyen3873
@quynhnguyen3873 15 сағат бұрын
Hoặc giảm số Mũ đưa về A^2-B^2
@prollysine
@prollysine Күн бұрын
case 1 , -ln2/4= -2*ln2*x*e^(-2*ln2*x) , /4/4 * -ln2/4 = 4*-ln2/16 , --> (4*-ln2)*e^((-ln2)^4) , (4*-ln2)*e^(4*-ln2) , / 4*-ln2=2*-ln2*x , -4=-2x , X1=2 , test x1 , OK , case 2 , W(-ln2/4)=-2*ln2*x , -0.2148111164=-2*ln2*x , x2=-0.2148111164/(2*ln2) , test x2 , OK ,
@SALogics
@SALogics 16 сағат бұрын
Very nice trick! ❤
@SGuerra
@SGuerra Күн бұрын
A questão é muito boa, mas eu demorei uns 10 minutos para encontrar uma solução simples e muito diferente da sua. Parabéns pela escolha. Brasil - Outubro de 2024. The question is very good, but it took me about 10 minutes to find a simple solution that is very different from yours. Congratulations on your choice. Brazil - October 2024.
@SALogics
@SALogics 16 сағат бұрын
muito obrigado! Por favor, compartilhe sua solução.❤
@LITHICKROSHANMS-gw2lx
@LITHICKROSHANMS-gw2lx Күн бұрын
I like it very much of solution
@SALogics
@SALogics 16 сағат бұрын
thank you so much! ❤
@نويصرنويصر
@نويصرنويصر Күн бұрын
You have to prove the hypothesis. a=7x²,b=7y²
@SALogics
@SALogics 14 сағат бұрын
Ok! ❤
@romybaul6053
@romybaul6053 Күн бұрын
If the original equation is transformed into an equation that has the one variable on one side of the equation and the other variable on the opposite side of the equation, we will have: b=(44-a^2)/(2a+1). From the above relationship, if we assign any value for "a", we will obtain a corresponding value for "b". Therefore, there are infinitely many pair of solutions for "a" and "b". Examples are: (a,b)=(0,44), (2,8), (3,5), (12,-4), (17,-7), (87,-43), (-1,-43),(-3,-7), (-4,-4), (-13,5), (-18,8), (-88,44) and so on.
@SALogics
@SALogics 14 сағат бұрын
Very nice trick! ❤
@cabasantbab
@cabasantbab Күн бұрын
2
@SALogics
@SALogics 14 сағат бұрын
Yes, you are right! ❤
@prollysine
@prollysine Күн бұрын
log(5)x * log(5)x = log(5)625 , 5^4=625 , log(5)625=4 , (log(5)x)^2=2^2 , log(5)x=+/-2 , x= 5^2 , 5^(-2) , x= 25 , 1/25 ,
@SALogics
@SALogics 14 сағат бұрын
Very nice trick! ❤
@prollysine
@prollysine 11 сағат бұрын
@@SALogics Thanks!
@ВладимирКоваленко-щ6д
@ВладимирКоваленко-щ6д 2 күн бұрын
Если знать таблицу квадратных чисел, то такую задачу можно решить за несколько сикунд 25^2=625
@SALogics
@SALogics 14 сағат бұрын
ты прав! ❤
@КонстантинШарашов
@КонстантинШарашов 2 күн бұрын
x=(-3) ?
@MyOneFiftiethOfADollar
@MyOneFiftiethOfADollar 2 күн бұрын
The method used is rather famously called completing the product or SFFT(Simons favorite factoring trick) Great way create common binomial factors. thanks
@SALogics
@SALogics 14 сағат бұрын
You are very welcome! ❤
@trojanleo123
@trojanleo123 2 күн бұрын
x = 2
@SALogics
@SALogics 14 сағат бұрын
You are right! ❤
@trojanleo123
@trojanleo123 2 күн бұрын
x = (25 , 1/25)
@SALogics
@SALogics 14 сағат бұрын
You are right! ❤
@ChavoMysterio
@ChavoMysterio 2 күн бұрын
x^[log_5(x)]=625 [5^[log_5(x)]]^[log_5(x)]=625 Let n=log_5(x) (5ⁿ)ⁿ=625 5^(n²)=5⁴ n²=4 |n|=2 n=-2 log_5(x)=-2 x=5^-2 x=0.04 ❤ n=2 log_5(x)=2 x=25 ❤
@SALogics
@SALogics 14 сағат бұрын
Very nice trick! ❤
@aminimam5118
@aminimam5118 2 күн бұрын
W(-(ln4)/8)=W(-ln8xe^(-ln8x)) gives both solution simultaneously
@SALogics
@SALogics 14 сағат бұрын
Ok, i will check! ❤
@yakupbuyankara5903
@yakupbuyankara5903 2 күн бұрын
X=25
@SALogics
@SALogics 14 сағат бұрын
You are right! ❤
@yakupbuyankara5903
@yakupbuyankara5903 2 күн бұрын
M=-1/4
@SALogics
@SALogics 14 сағат бұрын
You are right! ❤
@nasrullahhusnan2289
@nasrullahhusnan2289 2 күн бұрын
Note that there are two unknowns in the equation. With no constraint being imposed there are many solution. If (x,y) is a pair of integer the trivial solutions: (x^y)-y=77 =78¹-1 --> (x,y) --> (78,1) =1^(-76)-(-76) --> (1,-76) Other solution: (x^y)-y=81-4 (x^y)-y=3⁴-4 --> (x,y)=(3,4) by comparing the structure. The general approach is [x^(½y)]²-(y^½)²=77 [x^(½y)+(y^½)][x^(½y)-(y^½)]=7×11 x^(½y)+y^½=11 x^(½y)-y^½=7 Half of the sum is x^(½y)=9 Half of the difference is y^½=2 --> y=4. Hence x=3 --> (x,y)=(3,4 ) Thus (x,y)={(-1,76),(3,4),(78,1)}
@SALogics
@SALogics 14 сағат бұрын
Very nice! ❤
@SGuerra
@SGuerra 2 күн бұрын
Que que você fez uma questão bonita. Parabéns 👏👏👏👏👏
@SALogics
@SALogics 14 сағат бұрын
muito obrigado! ❤
@victorchoripapa2232
@victorchoripapa2232 2 күн бұрын
X=-1/3
@victorchoripapa2232
@victorchoripapa2232 2 күн бұрын
Solution 27^x+x=0 27^x=-x Let's do: -x=u --> x=-u Then: 27^(-u)=u 27=u^(-1/u) 27=(1/u)^(1/u) 3^3=(1/u)^(1/u) Then: 3=1/u --> u=1/3 And x=-u --> x=-1/3
@victorchoripapa2232
@victorchoripapa2232 2 күн бұрын
Verifying that: 27^(-1/3)+(-1/3)= (1/27)^(1/3)-1/3= 1/3-1/3= 0
@SALogics
@SALogics 14 сағат бұрын
You are right! ❤
@FredJehomiah
@FredJehomiah 2 күн бұрын
You solve in a unique way different from other pls can you solve the equation below a + b + c = 6 a² + b² + c² = 14 a⁸ + b⁸ + c⁸ = ?
@SALogics
@SALogics 14 сағат бұрын
Yes of course! ❤
@DJ.Nihad6174
@DJ.Nihad6174 2 күн бұрын
First method >>>>>>
@SALogics
@SALogics 2 күн бұрын
Very nice! ❤
@LITHICKROSHANMS-gw2lx
@LITHICKROSHANMS-gw2lx 2 күн бұрын
Good effort
@SALogics
@SALogics 2 күн бұрын
Thank you so much! ❤
@jasperkok8745
@jasperkok8745 2 күн бұрын
The first method gives 2 answers, while the second method only gives one. So what about the first answer that resulted from method 1? Is it to be rejected, or doesn’t method 2 give all the correct answers?
@ZionV-d5m
@ZionV-d5m 2 күн бұрын
Excelente solución
@SALogics
@SALogics 2 күн бұрын
Thanks and welcome! ❤
@LITHICKROSHANMS-gw2lx
@LITHICKROSHANMS-gw2lx 2 күн бұрын
Nice solution sir
@SALogics
@SALogics 2 күн бұрын
Thanks and welcome! ❤
@sy8146
@sy8146 2 күн бұрын
There are infinite solutions. (x, y) = (78, 1), (√79, 2), (80^(1/3), 3), (3, 4), (82^(1/5), 5), (83^(1/6), 6), ・・・ [ (-3, 4) is also one of the solutions. ]
@sidharthpatra4751
@sidharthpatra4751 2 күн бұрын
A single equation in 2 variables will always have infinite solutions. I think a part of the question is not mentioned, may be
@SALogics
@SALogics 2 күн бұрын
You are right! ❤