25（x+y）二次方-16（x-y）二次方=[5(x+y)]²-[4(x-y)]²=(5x+5y)²-(4x-4y)²=(5x+5y+4x-4y)(5x+5y-4x+4y)=(9x+y)(x+9y)x二次方-4y二次方+x+2y=(x+2y)(x-2y)+(x+2y)=(x+2y)(x-2y+1)（x+2）（x+4)+x...