a) (-1) + 2 + (-3) + 4 + .... + (-2009) + 2010

= (-1 + 2) + (-3 + 4) + ..... + (-2009 + 2010)

= -1 + (-1) + (-1) + .... + (-1) 

= -1 . 1005 = -1005

b) 1 + (-2) + (-3) + 4 + 5 + (-6) + (-7) + 8 + ... + 2005 + (-2006) + (-2007) + 2008

= [1 + (-2) + (-3) + 4] + [5 + (-6) + (-7) + 8 ] + ..... + [2005 + (-2006) + (-2007) + 2008]

= 0 + 0 + ...... + 0 = 0

ghe

a) Ta có: \(\left(-1\right)+2+\left(-3\right)+4+...+\left(-2009\right)+2010\)

\(=1+1+...+1\)

=1005

b) Ta có: \(1+\left(-2\right)+\left(-3\right)+4+5+\left(-6\right)+\left(-7\right)+8+...+2005+\left(-2006\right)+\left(-2007\right)+2008\)

\(=\left(1-2-3+4\right)+\left(5-6-7+8\right)+...+\left(2005-2006-2007+2008\right)\)

=0

\(\frac{\text{2006 x 125 + 1000}}{\text{ 2005 x 126 - 880}}=???\)

Trả lời :

\(\frac{\text{2006 x 125 + 1000}}{\text{2005 x 126 - 880}}=\frac{\text{251750}}{\text{251750}}=1\)

Chúc bạn học tốt !

Lahh dsr uẹđb bh s

\(B=\frac{2006\cdot125+1000}{126\cdot2005-880}\)

= \(\frac{2005\cdot125+125+1000}{2005\cdot126-880}=\frac{2005\cdot125+1125}{2005\cdot126-880}\)

=\(\frac{2005\cdot125+1125}{2005\cdot125+125-880}=1,007523912\)

a,  ( 32,5 + 28,3 X 2,7 - 108,91 ) X 2006
= (32,5 + 76,41 - 108,91)X 2006
= (108,91 - 108,91) X 2006
= 0 X 2006
= 0

b, \(\frac{2006.125+1000}{126.2005-880}=\frac{2005.125+125+1000}{125.2005+2005-880}=\frac{2005.125+1125}{125.2005+1125}=1\)

a: \(=\dfrac{3}{7}+\dfrac{7}{8}+\dfrac{4}{7}-\dfrac{15}{8}=1-1=0\)

b: \(=\dfrac{1}{2}+\dfrac{4}{5}+\dfrac{3}{8}-\dfrac{7}{40}+\dfrac{1}{2}\)

\(=1+\dfrac{32+15-7}{40}=1+1=2\)

( 125³ . 7⁴  - 5⁹ . 49² ) : 2005²⁰⁰⁶

= [ ( 5³ )³ . 7⁴ - 5⁹ . ( 7² )² ] : 2005²⁰⁰⁶

= [ 5⁹ . 7⁴ - 5⁹ . 7⁴ ] : 2005²⁰⁰⁶

= 0 : 2005²⁰⁰⁶

= 0

cảm ơn nha 

1:

a: \(=\dfrac{-4}{7}+\dfrac{4}{7}+\dfrac{3}{7}-\dfrac{23}{34}-\dfrac{4}{5}=\dfrac{3}{7}-\dfrac{23}{34}-\dfrac{4}{5}=-\dfrac{1247}{1190}\)

b:

Sửa đề: \(\dfrac{-5}{13}+\dfrac{4}{19}+\dfrac{-8}{13}+\dfrac{15}{19}+\dfrac{45}{6}\) 

\(=\dfrac{-5}{13}-\dfrac{8}{13}+\dfrac{4}{19}+\dfrac{15}{19}+\dfrac{45}{6}=\dfrac{9}{2}\)

251750

251742

\(\frac{2006\cdot125+1000}{126\cdot2005-888}=\frac{2005\cdot125+125+1000}{125\cdot2005+2005-888}=\frac{2005\cdot125+1125}{125\cdot2005+1117}\)

=> không tính nhanh được

\(\frac{125875}{125871}\)