2（6X方+X）方-11（6X方+X）+5=[2(6x²+x)-1][(6x²+x)-5]=(12x²+2x-1)(6x²+x-5)
=(12x²+2x-1)(6x-5)(x+1)
X四次方-10X方+9=(x²-1)(x²-9)=(x-1)(x+1)(x-3)(x+3)
X三次方-7X方+12X=x(x²-7x+12)=x(x-3)(x-4)
（X+Y)方+2(X+Y)-15=(x+y+5)(x+y-3)
A四次方-21A方-100=(a²-25)(a²+4)=(a-5)(a+5)(a²+4)
（X方+X）方-14（X方+X）+24=(x²+x-2)(x²+x-12)=(x-1)(x+2)(x-3)(x+4)
X方（X-1）-Y方（X-1)=(x-1)(x²-y²)=(x-1)(x-y)(x+y)