原式=[(x+1)(x+4)][(x+2)(x+3)]-24
=[(x²+5x)+4][(x²+5x)+6]-24
=(x²+5x)²+10(x²+5x)+24-24
=(x²+5x)²+10(x²+5x)
=(x²+5x)(x²+5x+10)
=x(x+5)(x²+5x+10)
原式=[(x+1)(x+4)][(x+2)(x+3)]-24
=[(x²+5x)+4][(x²+5x)+6]-24
=(x²+5x)²+10(x²+5x)+24-24
=(x²+5x)²+10(x²+5x)
=(x²+5x)(x²+5x+10)
=x(x+5)(x²+5x+10)