Question

化简【(x+y)^2-2(x-y)^2+(x+2y)(x-2y)】÷y，其中x=2,y=-1

Answer 1

【(x+y)^2-2(x-y)^2+(x+2y)(x-2y)】÷y
=[x²+2xy+y²-2(x²-2xy+y²)+(x²-4y²)]÷y
=(x²+2xy+y²-2x²+4xy-2y²+x²-4y²)÷y
=(6xy-5y²)÷y
=6x-5y
当 x=2，y=-1时
原式=12+5=17

Answer 2

【(x+y)^2-2(x-y)^2+(x+2y)(x-2y)】÷y
=(x²+2xy+y²-2x²-2y²+4xy+x²-4y²)÷y
=(6xy-5y²)÷y
=6x-5y
=6×2-5×(-1)
=17

Answer 3

直接带入阿。