已知x,y满足x-2y=0,求(2x²-3y²)/(x²+5y²).
问题描述:
已知x,y满足x-2y=0,求(2x²-3y²)/(x²+5y²).
答
x-2y=0
x=2y
(2x²-3y²)/(x²+5y²)
=(2*4y²-3y²)/(4y²+5y²)
=5y²/9y²
=5/9