(1)a^2b^2+16ab+39
1 13
x
13
=(ab+13)(ab+3)
(2)15x^2n+7x^ny^n+1-4y2n+2
5 -4
x
31
=(5x^n -4y^n+1)(3x^n+ y^n+1)
(3)（x^2+3x）^2-22（x^2+3x）+72
1 -4
x
1 -18
=[（x^2+3x）-4]* [（x^2+3x）-18]
1416
x x
1-1 1-3
=(x+4)(x-1)(x+6)(x-3)