x五次方-x＝x(x^4-1)=x(x^2+1)(x+1)(x-1)
9x四次方-36y平方=9(x^2+2y)(x^2-2y)
9(2a+b)平方-24（2a+b)(3a-b)+16(3a-b)平方
=[3(2a+b)]^2-2*[3(2a+b)]*[4(3a-b)]+[4(3a-b)]
=[3(2a+b)-4(3a-b)]^2
=(7b-6a)^2
x平方（4x-3y)+(3y-4x)=(x^2-1)(4x-3y)=(x+1)(x-1)(4x-3y)
x四次方-2x三次方-35x平方=x^2(x-7)(x+5)
25（x-2y)平方-4(2y-x)平方=21(x-2y)^2
x平方-4xy-1+4y平方=(x^2-4xy+4y^2)-1=(x-2y)^2-1=(x-2y+1)(x-2y-1)