十字相乘练习5x^2+7x-62x^2+15x+76y^2-11y-10m^2x^2-8mx+12(m+n)^2-(m+

5x^2+7x-6
=(5x-3)(x+2)
2x^2+15x+7
=(2x+1)(x+7)
6y^2-11y-10
==( 2y-5)(3y+2)
m^2x^2-8mx+12
=(mx-2)(mx-6)
(m+n)^2-(m+n)-30
=(m+n-6)(m+n+5)
x^4-7x^2-18
=(x^2-9)(x^2+2)
=(x+3)(x-3)(x^2+2)
10(x+2)^2-29(x+2)+10
=[5(x+2）-2][2(x+2）-5]
=(5x-8)(2x-1)
(x^2-4x)^2-(x^2-4x)-20
=(x^2-4x-5)(x^2-4x+4)
=(x-5)(x+1)(X+2)^2
(a^2+5a+3)(a^2+5a-2)-6
=(a^2+5a)^2+(a^2+5a)-6-6
=(a^2+5a)^2+(a^2+5a)-12
=(a^2+5a+4)(a^2+5a-3).