(a-2)[(a-2)^2+6a]+(a+3)[(a+3)^2-9a] 计算

来源：百度知道 编辑：UC知道 时间：2024/06/30 19:05:03
还有2道
1：已知x(x-1)-(x^2-y)=-2,求x^2+y^2/2-xy的值
2：（x^2-3)^2-12(x^2-3)+36 因式分解

1)
x(x-1)-(x^2-y)=-2
x^2-x-x^2+y=-2
x-y=2
(x-y)^2=4
x^2+y^2-2xy=4
x^2+y^2=4+2xy

(x^2+y^2)/2-xy=2+xy-xy=2

2)
（x^2-3)^2-12(x^2-3)+36
=[(x^2-3)-6]^2
=(x^2-9)^2
=(x-3)^2(x+3)^2

(a-2)[(a-2)^2+6a]+(a+3)[(a+3)^2-9a]
=(a-2)(a^2+2a+4)+(a+3)(a^2-3a+9)
=a^3+2a^2+4a-2a^2-4a-8+a^3-3a^2+9a+3a^2-9a+27
=2a^3+19
1.x(x-1)-(x^2-y)=-2
x^2-x-x^2+y=-2
x-y=2
(x-y)^2=4
x^2+y^2-2xy=4
x^2+y^2=4+2xy
(x^2+y^2)/2-xy=2+xy-xy=2
2.（x^2-3)^2-12(x^2-3)+36
=[(x^2-3)-6]^2
=(x^2-9)^2
=(x-3)^2(x+3)^2