tính nhanh
a, (756 - 217) - ( 183 -44)
\(=756-217-183+44\)
\(=\left(756+44\right)+\left(-217-183\right)\)
\(=800-400\)
\(=400\)
b, 11-12+13-14+15-16+17-18+19-20
\(=\left(11+19\right)-\left(12+18\right)+\left(13+17\right)-\left(14+16\right)+\left(15-20\right)\)
\(=30-30+30-30-5\)
\(=-5\)
a) \(\left(756-217\right)-\left(183-44\right)\)
= \(756-217-183+44\)
= \(\left(756+44\right)+\left(-217-183\right)\)
= \(800+\left(-400\right)\)
= \(400\)
b) 11-12+13-14+15-16+17-18+19-20
= (11-12) +(13-14)+(15-16)+(17-18)+(19-20)
=11-12= -1
Mà: có 5 cặp số
Nên: -1*5= -5
nha
c) 101 - 102 - (-103) -104-(-105) - 106 - (-107) - 108 - ( -109)-110
= 101 -102 +103 -104 +...+ 109-110 (có 10 sô)
= -1+(-1) +...+ (-1) (có 5 nhóm)
= -1 .5
= -5
