9(a-b)²+12(a²-b²)+4(a+b)²
=(3(a-b))+2*3*2(a+b)(a-b)+(2(a+b))²
=(3(a-b)+2(a+b))²
=(5a-b)²
a³-10a²+25a
=a(a²-2*5*a+5²)
=a(a-5)²
x²+2x+1-y²
=(x+1)²-y²
=(x+1+y)(x+1-y)
25（m+n-3）²-9（3m-2n）²
=(5(m+n-3))²-(3(3m-2n))²
=(5(m+n-3)+3(3m-2n))(5(m+n-3)-3(3m-2n))
=(14m-n-15)(-4m+11n-15)