已知4x^2-9y^2=48,-2x+3y=4.求-2x-3y的值
问题描述:
已知4x^2-9y^2=48,-2x+3y=4.求-2x-3y的值
答
4x^2-9y^2=48
(2x+3y)(2x-3y)=48
-(2x+3y)(3y-2x)=-48
-4(2x+3y)=-48
2x+3y=12
-2x-3y=-12