Question

先化简，再求值(x+y)(x-y)+(x²-2xy+y²)-(x²y)³÷(x²y)²其中x=1,

先化简，再求值(x+y)(x-y)+(x²-2xy+y²)-(x²y)³÷(x²y)²其中x=1,y=2

Answer 1

（x+y）（2x-y）-（x+2y）（x-2y）坦让=2x 2 -xy+2xy-y 2 -（x 2 -4y 2 ）=2x 2 -xy+2xy-y 2 -x 2 +4y 2 =x 2 +xy+3y 2 ；把罩山x=3，y=4代入得，原式物信中=3 2 +3×4+3×4 2 =9+12+3×16=21+48=69．

Answer 2

Answer 3

题干不详

Answer 4

y（x-y)-x(x+y)/x²-y² ÷ x²+y²/x+y
=xy-y²-x²-xy/x²-y²÷ x²+y²唯迹拿/x+y
=x²+y²/x²-y²×x+y/x²州纳+y²
=x+y/x²指搭-y²
=1/x-y
=1/3