设点C(2a-1,a+2)在点A(1,-3),B(8,-1)所在直线上,求a
问题描述:
设点C(2a-1,a+2)在点A(1,-3),B(8,-1)所在直线上,求a
答
运用斜率得:
(-3+1)/(1-8)=(a+2+1)/(2a-1-8)
(-2)/(-7)=(a+3)/(2a-9)
7a+21=4a-18
3a=-39
a=-13