(1)x^4-7x^2y^2+9y^4
2个回答

1.原式=x^4-7x^2y^2+10y^4-y^4

=(x^2-2y^2)(x^2-5y^2)-y^4

=[x^2-2y^2)+y^2][(x^2-5y^2)-y^2]

=(x^2-2y^2+y^2)(x^2-5y^2-y^2)

2.原式=(y^3+17y^2)-(3y+51)

=y^2(y+17)-3(y+17)

=(y^2-3)(y+17)

3.原式=x^2(y-z)-4(y-z)-3x(z-y)

=x^2(y-z)-4(y-z)+3x(y-z)

=(x^2+3x-4)(y-z)

=(x+4)(x-1)(y-z)

4.原式=7(a-3)^2+3(a-3)-4

=[(a-3)+1][7(a-3)-4]

=(a-2)(7a-21-4)

=(a-2)(7a-25)