已知x,y满足x-2y=0,求(2x²-3y²)/(x²+5y²).
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已知x,y满足x-2y=0,求(2x²-3y²)/(x²+5y²).
已知x,y满足x-2y=0,求(2x²-3y²)/(x²+5y²).
已知x,y满足x-2y=0,求(2x²-3y²)/(x²+5y²).
x-2y=0
x=2y
(2x²-3y²)/(x²+5y²)
=(2*4y²-3y²)/(4y²+5y²)
=5y²/9y²
=5/9
x-2y=0
x=2y
(2x²-3y²)/(x²+5y²)
=[2*(2y)²-3y²]/[(2y)²+5y²]
=[8y²-3y²]/[4y²+5y²]
=[5y²]/[9y²]
=5/9
63
x-2y=0
x=2y
将x=2y代入(2x²-3y²)/(x²+5y²)得
(2*4y²-3y²)/(4y²+5y²)
=5y²/9y²
=5/9
x=2y代进去,很简单的。
由x-2y=0推出x=2y
所以2x²=8y²分子变为5y²
同理分母变为4y²+5y²=9y²
原式=九分之五
因为x-2y=0,所以x=2y
x²=4y²
(2x²-3y²)/(x²+5y²)
=5y²/9y²
=5/9
因为x-2y=0,所以x=2y。
(2x²-3y²)/(x²+5y²)
={(2(2y)²-3y²)}/ {(2y)²+5y²}
=5x²/9y²
=5/9
因为x-2y=0,所以x=2y,
(2x²-3y²)/(x²+5y²)
=(2(2y)²-3y²)/((2y)²+5y²)
=(8y²-3y²)/(4y²+5y²)
=5y²/9y²
=5/9