Question

1、x的2m+4次方-x的m+3次方-72x的2次方y的2次方

Answer 1

1? x^2[x^ (2m+2) -x^(m+1)-72y^2)]

2,6x^2-5xy-6y^2=(3x+2y)(2x-3y)

3,18x^2-21xy+5y^2=(3x-y)(6x-5y)

4,(x+1)(x+3)(x+5)(x+7)+15=(x^2+8x+7)(x^2+8x+15)+15

=(x^2+8x)^2+22(x^2+8x)+120

=(x^2+8x+12)(x^2+8x+10)

=(x+2)(x+6)(x^2+8x+10)