已知x+y=10,求[(x+y)^2-(x-y)^2-2y(x-y)]÷5y的值
问题描述:
已知x+y=10,求[(x+y)^2-(x-y)^2-2y(x-y)]÷5y的值
答
[(x+y)²-(x-y)²-2y(x-y)]÷5y
=[X²+2XY+Y²-X²+2XY-Y²-2XY+2Y²]÷5Y
=[2Y(X+Y)]÷5Y
=2/5(X+Y)
=2/5(10)
=4