Question

tính nhanh

\(a,1+3-5-7+9+11-.....-397-399\)

\(b,1.2.3....9-1.2.3...8-1.2.3....7.8^2\)

\(c,1152-\left(374+1152\right)+\left(-65+344\right)\)

Answer 1

\(b,1.2.3...9-1.2.3...8-1.2.3...7.8^2\)

\(=(1.2.3...8).(9-1-8)\)

\(=(1.2.3...8).0\)

\(=0\)

Answer 2

a,

= (1 + 3 - 5 - 7) + (9 + 11 - 13 - 15) + ... + (393 + 395 - 397 - 399)

= (-8) + (-8) + ... + (-8)

= (-8) . 50 (vì có 50 lần số hạng -8)

= - 400

_Vậy

Answer 3

b, 1 . 2 . 3 ... 9 - 1 . 2 . 3 ... 8 - 1 . 2 . 3 ... 7 . 8²

= (1 . 2 . 3 ... 8) (9 - 1 - 8)

= (1 . 2 . 3 ... 8) . 0

= 0

Answer 4

c, 1152 - (374 + 1152) + (-65 + 344)

= 1152 - 374 - 1152 + (-65) + 344

= (1152 - 1152) + [(-374) + 344 + (-65)]

= 0 + [(-3) + (-65)]

= -68