(x+y)²=x²+2xy+y² (x-y)²=x²-2xy+y²
∴(x+y)²-(x-y)²=4xy
∴(x+y)²-(x-y)²+4xy=8xy
[(x+y)2-(x-y)2+4xy] ÷(-2x)=8xy÷(-2x)=-4y
【问题补充】:(x+y)²=x²+2xy+y²
(x+y)^2-(x-y^2)+4xy=x²+6xy+2y²-x
[(x+y)^2-(x-y^2)+4xy] ÷(-2x)=( x²+6xy+2y²-x)÷(-2x)= -x/2-3y-(y²/x) +1/2
感觉题目可能写错了
原式=(x^2+2xy+y^2-x+y^2+4xy)/(-2x)
=(x^2+6xy+2y^2-x)/(-2x)
=(-1/2)x-3y-(y^2)/x+1/2
你那个是"2",还是平方啊?
[(x+y)2-(x-y2)+4xy] ÷(-2x)
=【x²+2xy+y²-x²+2xy-y²+4xy】÷(-2x)
=【2xy+2xy+4xy】÷(-2x)
=8xy÷(-2x)
=-4y