成都中考几何压轴题,经典模型的新考法!

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火星课堂

火星课堂

Күн бұрын

Пікірлер: 8
@georiashang1120
@georiashang1120 3 ай бұрын
如果你信任你的代数功底,这题有种不废脑只废稿的解法,今AE=y,BD=x;根据两组三角形相似,你可以得一方程组,其中一个y^2=2x+4可直接代入另一组,最后可得一个一元三次方程x^3+x^2-6x-8=0;因式分解它可得(x^2-x-4)(x+2)=0;去掉两组负根,得正解答案。
@strikerleecy126
@strikerleecy126 3 ай бұрын
家里有亲戚今年中考,正好说这题做不来。我后来看了下想了两种方法,第一个是连接BE有两个相似三角形CED和CEB,然后看到角平分线就想到延长AD再过C作AB平行线交F,这样三角形CFD和ADB也相似。这样设CB和CA为x和y的话可以根据两个相似和勾股定理搞出一个二元三次方程,但只要掌握点技巧的话可以发现那个方程组可以拿y²=x+k这种整体消元消掉y,剩下的三次方程组(关于x的)常数项是0。结果就是个一元二次方程了。连想带算算了花了20分钟左右,主要是第一次算错了常数项没消掉又看一元三次不能因式分解。第二种方法就看有个直角就直接建系设点列式化简(虽然好像是高中内容)C为原点,直接设AC长度b,BC长度a,然后用余弦定理列出角相等,然后E点因为是AD中点可以写坐标,这样EB长度也能表达让它和BC相等。这样同样也是和上面那种整体换元,然后得到一个常数项为0的一元三次方程当一元二次解。这下连想带算(其实根本没啥可以想的)大概花了7分钟算出来的。感觉我想的这两个方法算起来1要特别仔细2是得对自己的过程和结果自信😂😂😂
@ymj5161
@ymj5161 3 ай бұрын
有点难想
@clcmlxl
@clcmlxl 3 ай бұрын
题目没说AE=ED啊
@我的訴求就是121個訂閱
@我的訴求就是121個訂閱 3 ай бұрын
他證出來的
@weilu639
@weilu639 3 ай бұрын
他说了E是AD的中点。听题要仔细。
@Xinhe_LeinaliMyBeloved
@Xinhe_LeinaliMyBeloved 3 ай бұрын
😢我也是直接看题 傻了半天😢
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