3a(a+b)^2-27ab^2=?1/7(x-y)^3+7(y-x)=?(a+2b)^4-(a-2b)^4=?1/2x^2-18=?

3a(a+b)^2-27ab^2=?1/7(x-y)^3+7(y-x)=?(a+2b)^4-(a-2b)^4=?1/2x^2-18=?
3a(a+b)^2-27ab^2=?1/7(x-y)^3+7(y-x)=?(a+2b)^4-(a-2b)^4=?1/2x^2-18=?

3a(a+b)^2-27ab^2=?1/7(x-y)^3+7(y-x)=?(a+2b)^4-(a-2b)^4=?1/2x^2-18=?
原式=3a[(a+b)^2-9b^2]
=3a(a+b+3b)(a+b-3b)
=3a(a+4b)(a-2b)
原式=1/7(x-y)[(x-y)^3-49]
=1/7(x-y)(x-y+7)(x-y-7)
原式=[(a+2b)^2+(a-2b)^2][(a+2b)^2-(a-2b)^2]
=(2a^2+8b^2)(a+2b+a-2b)(a+2b-a+2b)
=16ab(a^2+4b^2)
原式=1/2(x^2-36)
=1/2(x+6)(x-6)

3a(a+b)^2-27ab^2
=3a[(a+b)^2-9b^2]
=3a(a+b+3b)(a+b-3b)
=3a(a+4b)(a-2b)
1/7(x-y)^3+7(y-x)
=1/7(x-y)[(x-y)^3-49]
=1/7(x-y)(x-y+7)(x-y-7)
(a+2b)^4-(a-2b)^4
=[(a+2b)^2+(a-2b)^2][(a+2b)^2-(a-2b)^2]
=(2a^2+8b^2)(a+2b+a-2b)(a+2b-a+2b)
=16ab(a^2+4b^2)
1/2x^2-18
=1/2(x+6)(x-6)