Question

Tinh nhanh:1+3-5-7+9+11-....-397-399

ai lam nhanh nhat mik tick cho1 giai chi tiet ra nhe

Answer 1

= (1+3-5-7) + (9+11-13-15) + ... + (393+395-397-399) 
 = -8+ (- 8) + .... (- 8) (có 50 số -8) 
= -8*50 
= -400

Answer 2

A=1+3-5-7+9+11-...-397-399

A = (1+3-5-7) + (9+11-13-15) + ... + (393+395-397-399) 
A = -8 - 8 - .... - 8 
A = -8*50 
A = -400

Answer 3

Tinh nhanh:1+3-5-7+9+11-....-397-399=400