x方（x+2）方-7x(x+2)-8x(x+2) -8\ / \// \/ \x(x+2) 1__________________-8x(x+2) + x(x+2) =-7x(x+2)所以x方（x+2）方-7x(x+2)-8=(x(x+2)-8)(x(x+2)+1)=(x²+2x-8)(x²+2x+1)同样的十字相乘法=(x+4)(x-2)(...