2个十字相乘的,(a+2b)^2-(a-2b)^25am^4-5an^4

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2个十字相乘的,(a+2b)^2-(a-2b)^25am^4-5an^4
2个十字相乘的,
(a+2b)^2-(a-2b)^2
5am^4-5an^4

2个十字相乘的,(a+2b)^2-(a-2b)^25am^4-5an^4
(a+2b)^2-(a-2b)^2
=[(a+2b)-(a-2b)][(a+2b)+(a-2b)]
=4b*2a
=8ab
5am^4-5an^4
=5a(m^4-n^4)
=5m(m^2+n^2)(m^2-n^2)
=5m(m^2+n^2)(m+n)(m-n)

答:
1.原式
=(a+2b+a-2b)(a+2b-a+2b)
=2a*4b
=8ab
2.原式
=5a(m^4-n^4)
=5a(m^2+n^2)(m^2-n^2)
=5a(m^2+n^2)(m+n)(m-n)