9(a-b)²+12(a²-b²)+4(a+b)²
2个回答

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)