406坤飞
幼苗
共回答了27个问题采纳率:96.3% 举报
4x²+9(kx+m)²=36
(4+9k²)x²+18kmx+(9m²-36)=0
由韦达定理:
x1+x2=-18km/(4+9k²)
x1x2=(9m²-36)/(4+9k²)
因为A2A⊥A2B(A(a,0)
[(-y1)/(x1-a)][(-y2)/x2-a)]=-1
y1y2+x1x2-a(x1+x2)+a²=0
y1y2=(kx1+m)(kx2+m)=k²x1x2+m(x1+x2)+m²
(1+k²)x1x2++(m-a)(x1+x2)+(a²+m²)=0
(1+k²)(9m²-36)/(4+9k²)+(m-a)[-18km/(4+9k²)]+(a²+m²)=0
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1年前
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