Finding the equation of a tangent line. Reddit calculus r/askmath

[@Mike__B]

I'm so happy I teach physics instead of math, now I can say "since you guys already took calculus 1 you know how to take the derivative of this function" and then I look at the practical application of what the derivative represents, e.g. the velocity or whatever.

[@lolidemon3163]

Ngl one of my college professors said that science is just math with names/labels attached to it

[@reedoken6143]

​@@lolidemon3163 bio is applied chem. chem is applied phys. phys is applied maths.

[@sohidulislam6020]

​@@lolidemon3163Science is just application of math in the real world

[@Tabu11211]

Derivative is just fancy subtraction ;)

[@lamemelord]

@@sohidulislam6020 me in middle school be like: that exists?

[@zeinbotak]

0:43 " ... and the direction says: that's the definition of derivative, which is this one right here!" Me watching in 240p: "yeah I see that!"

[@bprpcalculusbasics]

😂

[@urble]

The audio for this video is a little out of sync :/

[@ArthurvanH0udt]

Why not just use derivative of f(x) which is -2x-15 put in 7 and slope is -29. Why do the more difficult “h” thing?

[@OSW656]

The question asks you to do the question using the definition of derivative, So you have to follow the rules,no shortcuts allowed.

[@piccolo64]

For fun, after finding slope -29 i used parametric equation: {x = 7 + t {y = - 151 - 29t solve t for x = 0 7 + t = 0 t = - 7 then y = - 151 - 29*(- 7) = 52 (intercept) so tangent is: y= - 29x + 52 😊

[@kaamilverma1602]

This can also easily done by coordinate, slope of a line y = 4a(x-h)^2 is just First we will have to bring equation into above format but after that its really simple yy1 = 2a(x+x1) Since we know y1 and x1, we can simply plug in and while plugging in we can shift the x coordinate by x + h to get the final result

[@kaamilverma1602]

Not slope i wanted to say Tanget

[@OrenLikes]

6:03 the **formula** for the tangent line... :)

[@suyunbek1399]

i still don't get it, how did he get y=-29x+150 instead of y=-29x+52 its not like he just forgot the y1 and assumed it was 0 because then it would have been y=-29x+203 so he assumed it was -43 instead of -151? i suppose he calculated (-x)^2 instead of -x^2 cause then it would have been 49-105+3=-(105-52)=-53 and then he also miscalculated that to be -43, or he miscalculated 15*7 to be 95 something like that i guess. so mistake in calculations which is mnemonics problem + wrong sign which is familiarity with notation problem...

[@jinja3113]

Why -43? If he miscalculated (-x)^2 then he gets -53 and that's what makes it 203-53 = +150

[@bjorneriksson2404]

I think you're right with the miscalculation of the square, getting 49 instead of -49. And that would be enough, since 203 - 53 is 150. (And as you can see, the difference between 150 and 52 is 98 = 2*49)

[@occasionalshredder]

Why not use the faster definition for derivatives of d/dx= x^n-1 or whatever it is exactly

[@wistfulgraph]

it’s not the definition of a derivative. What you just described is the power rule.

[@occasionalshredder]

@@wistfulgraph yeah but it’s the fastest way to solve derivatives

[@OrenLikes]

Edit: my mistake, ignore the following (I won't erase because there is a comment correcting me) 2:19 close the outer parentheses! :)

[@BigDBrian]

They're already closed. Count again.

[@OrenLikes]

@@BigDBrian you are absolutely correct! thank you for pointing it out!

[@narfwhals7843]

Audio sync issues again from beginning to around 2:35

[@bprpcalculusbasics]

Thanks for letting me know!

[@cdkw8254]

cool!

[@OrenLikes]

why use of "a" AND "x" = not just "x"?!?!?!? I expect more mistakes at the question, I'm at 0:01... I'm sure you will catch them all and overcome them!