先化简式子 x分之x²-y²÷(x-x分之2xy-y²)再求值,其中,x=2,y=-1)
问题描述:
先化简式子 x分之x²-y²÷(x-x分之2xy-y²)再求值,其中,x=2,y=-1)
答
x分之(x²-y²)÷[x- x分之(2xy-y²)]
=x分之(x²-y²)÷[ x分之(x²-2xy+y²)]
=x分之(x+y)(x-y) * [(x-y)²分之x]
=(x-y)分之(x+y)
=(2+1)分之(2-1)
=3分之1