Question

多项式因式分解:(25x²-36)

am+bm-cm

64-16a+a²

2(x-y)+a(x-y)

0.49x²-0.04y²

-4a²b+4ab-1

-3a³x+12ax³

m³n-2m²n²+mn³

分解因式：
(m-n)³+2n(n-m)²

1/2a³b+2a²b²+2ab³

已知a+b=-2,ab=-2/5.求a(a+b)(a-b)-a(a+b)²的值.

Answer 1

(25x²-36)=(5x)²-6²=(5x+6)(5x-6)

am+bm-cm

64-16a+a²=(8-a)²

2(x-y)+a(x-y)=(x-y)(2+a)

0.49x²-0.04y²=(0.7x+0.2y)(0.7-0.2y)

-4a²b+4ab-1=

-3a³x+12ax³=3ax(4x²-a²)=3ax(2x+a)(2x-a)

m³n-2m²n²+mn³=mn(m²-2mn+n²)=mn(m-n)²

分解因式：
(m-n)³+2n(n-m)²=(m-n)²(m-n+2n)=(m-n)²(m+n)

1/2a³b+2a²b²+2ab³=(1/2)ab(a²+4ab+4b²)=(1/2)ab(a+2b)²)

已知a+b=-2,ab=-2/5.求a(a+b)(a-b)-a(a+b)²的值.
a(a+b)(a-b)-a(a+b)²
=a(a+b)(a-b-a-b)
=-2ab(a+b)
=-2(-2/5)(-2)
=-8/5
=-1又3/5

追问

am+bm-cm

-4a²b²+4ab-1

已知a+b=-2,ab=-2/5.求a(a+b)(a-b)-a(a+b)²的值.这道题目我觉得是等于10.
能好好算算吗

追答

am+bm-cm=m(a+b-c)

-4a²b²+4ab-1=-(4a²b²-4ab+1)=-(2ab-1)²

a(a+b)(a-b)-a(a+b)²
=a³-ab²-(a³+2a²b+ab²)
=-ab²-2a²b-ab²
=-ab(b+2a+b)
=-2ab(a+b)
=-2(-2/5)(-2)
=-8/5
=-1又3/5