化简求值.1)(2xy-y)-(y+yx)其中x=2y=22)5(a^2b-3ab^2)-2(a^2b-7ab^2)其中a=-2b=-1

Question

化简求值.1)(2xy-y)-(y+yx)其中x=2 y=2 2)5(a^2b-3ab^2)-2(a^2b-7ab^2)其中a=-2 b=-1

Answer 1

(2xy-y)-(y+yx)其中x=2 y=2
=2xy-y-y-xy
=xy-2y
=2*2-2*2
=0
2)5(a^2b-3ab^2)-2(a^2b-7ab^2)其中a=-2 b=-1
=5a²b-15ab²-2a²b+14ab²
=3a²b-ab²
=ab(3a-b)
=(-2)(-1)(-6+1)
=-10