e) 1-2+3-4+5-6+...+199-200
=(1-2)+(3-4)+(5-6)+...+(199-200) (có 100 nhóm)
= (-1) + (-1) + (-1) +...+ (-1) (có 100 số -1)
=-100
f) 5.(-8).(-2).(-3)
=[5.(-2)].[(-8).(-3)]
=(-10).24
=-240
g) 3.(-5)²+2.(-5)-20
=3.(-5)²+2.(-5)-4.(-5)
=(-5).[3.(-5)+2-4]
=(-5).(-15-2)
=(-5).(-17)
=85