x四次方-29x²+100
=（x²-4)(x²-25)
=(x+2)(x-2)(x+5)(x-5)
-2x²z+24xyz-70y²z
=-2z(x²-12xy+35y²)
=-2z(x-5y)(x-7y)
（x+y）²-4（x+y）-12
=(x+y-6)(x+y+2)
x²+（k+2）x+（k+1）=(x+1)(x+k+1)
4a²b²-（a²+b²）²
=[2ab+(a²+b²)][2ab-(a²+b²)]
=-(a+b)²(a-b)²