Question

分解因式：(x+2y)^3-4(x-y)^2+4(x-y) 分解求值（3m-4n)^2+2(3m-4n)(3m+4n)-

Answer 1

1、(x+2y)^3-4(x-y)^2+4(x-y)

题目有问题吧,不可能展开,那么复杂

我觉得应该是(x-y)^3-4(x-y)^2+4(x-y)=(x-y)【(x-y)^2-4(x-y)+4】=(x-y)(x-y-2)^2

2、因为m=-2,n=1/4；所以（3m-4n）^2+2(3m-4n)(3m+4n)-3(3m+4n)^2

=9m^2-24mn+16n^3+18m^2-32n^2-27m^2-72mn-48n^2

=-96mn-64n^2

=-96*(-2)*1/4-64*(1/4)^2

=48-4

=44

3、因为a+b=1/2,ab=3/8

所以a^3b+2a^2b^2+ab^3

= ab(a^2+2ab+b^2)

= ab(a+b)^2

= 3/8 * (1/2)^2

= 3/32