Question

HỘ MÌNH VỚI Ạ

Bài 1: Tính

a, A= -1+3-5+7-9+... -2013+2015-2017

b, B= 2-4+6-8+...+2014-2016+2018

c. C= 1+2-3-4+5+6-7-8+...-111-112+113+114

Bài 2

a, ( x+1)+ (x+2)+ (x+3)+...+(x+100)= 5750

b, (2x-1)+(4x-2)+...+(400x-200)= 5+10+15+...+1000

c, ( x+2)+(4x+4)+(7x+6)+...+(25x+18)+ (28x+20)= 1560

Bài 3

a, 1*3+2*4+3*5+4*6+...99*101+100*102

b, 1*100+2*99+3*98+...+99*2+100*1

Answer 1

\(a,A=-1+3-5+7-9+...-2013+2015-2017=\left(-1+3\right)+\left(-5+7\right)+...+\left(-2013+2015\right)-2017\)\(=2+2+..+2-2017\)

\(=2.504-2017=-1009\)

\(b,B=2-4+6-8+...+2014-2016+2018\)\(=2+\left(-4+6\right)+\left(-8+10\right)+...+\left(-2016+2018\right)==2+2+...+2\)\(=2+503.2=1008\)