因式分解提,1.(a+3b)^2-5a-15b2.am-an-m^2+n^23.45m^2-20ax^2+20axy-5ay^2

Question

因式分解提,
1.(a+3b)^2-5a-15b
2.am-an-m^2+n^2
3.45m^2-20ax^2+20axy-5ay^2

Answer 1

1.(a+3b)^2-5a-15b
=(a+3b)^2-5(a+3b)
=(a+3b)(a+3b-5)
2.am-an-m^2+n^2
=a(m-n)-(m^2-n^2)
=a(m-n)-(m-n)(m+n)
=(m-n)(a-m-n)
3.45m^2-20ax^2+20axy-5ay^2
错了吧
应该是45am^2-20ax^2+20axy-5ay^2
=45am^2-5a(4x^2-4xy+y^2)
=45am^2-5a(2x-y)^2
=5a[9m^2-(2x-y)^2]
=5a(3m+2x-y)(3m-2x+y)
如果没错
则45m^2-20ax^2+20axy-5ay^2
=5(9m^2-4ax^2+4axy-ay^2)