如果2X-Y=10,求代数式[(X²+Y²)-(X-Y)²+2Y(X-Y)]÷4Y

题目

如果2X-Y=10,求代数式[(X²+Y²)-(X-Y)²+2Y(X-Y)]÷4Y

答案

[(X²+Y²)-(X-Y)²+2Y(X-Y)]÷4Y
=（x^2+y^2-x^2+2xy-y^2+2xy-2y^2)/4y
=(4xy-2y^2)/4y
=x-1/2y
如果2X-Y=10,
x-1/2y=10/2=5