已知y1=6-x,y2=2 7x. (1)当x取何值时，y1=2y2? (2)当x取何值时(1)y1=2y2:6-x=2*(2 7x) 15x=2 x=2/15 (2)y1比y2小-3 6-x
1. y1=6-x, y2=2+7x , y1=y2-3 6-x=2+7x-3 => 8x=7 => x= 7/8
即:y2-y1=-32+7x-6+x=-38x=1x=1/8
