(x+1)(x+4)-(x+2)∧2
=x²+5x+4-x²-4x-4
=x
1.x>0
(x+1)(x+4)>(x+2)∧2
2.x=0
(x+1)(x+4)=(x+2)∧2
3.x<0
(x+1)(x+4)<(x+2)∧2