Question

数学题求解，要过程

Answer 1

追答

求采纳

追问

第8题

追答

Answer 2

9、两个非负数和是0，那么
x+3=0，x=-3
x-y+10=0，y=7
x-y=-10
x+y=4
xy=-21
原式
=5x²y-[2x²y-3xy+x²y-3x²]-2xy²-y²
=5x²y-3x²y+3xy+3x²-2xy²-y²
=2x²y+3xy-2xy²+3x²-y²
=2xy(x-y)+3x(x+y)-y²
=2×(-21)×(-10)+3×(-3)×4-7²
=420-36-49
=335
8、原式
=-（x-y)²-4(x-y)+3(x-y)²-6(x-y)-2(x-y)²+7(x-y)
=(-1+3-2)(x-y)²+(-4-6+7)(x-y)
=-3(x-y)
=-3x+3y

追问

第8题

追答

8、原式
=-（x-y)²-4(x-y)+3(x-y)²-6(x-y)-2(x-y)²+7(x-y)
=(-1+3-2)(x-y)²+(-4-6+7)(x-y)
=-3(x-y)
=-3x+3y

追问

谢谢

Answer 3

Answer 4

追问

第8题

Answer 5

8= -(x-y)^2-4(x-y)+3(x-y)^2-6(x-y)-2(x-y)^2+7(x-y)
=-3x+3y
9 x+3=0 x-y+10=0 x=-3 y=7
原式=5x^2y-2x^2y+3xy-x^2y+3x^2-2xy^2-y^2
=2x^2y+3xy+3x^2-2xy^2-y^2
=335