A = \(\frac{1}{2}\)+ \(\frac{1}{2^2}\)+ \(\frac{1}{2^3}\)+ ... + \(\frac{1}{2^{10}}\)

2A = \(1\)+ \(\frac{1}{2}\)+ \(\frac{1}{2^2}\)+ ... + \(\frac{1}{2^9}\)

2A - A =  \(1\)- \(\frac{1}{2^{10}}\)

Vậy A = \(\frac{1023}{1024}\)

HÌNH NHƯ ĐỀ SAI 

BẠN COI LẠI ĐI

K MÌNH NHA!

...................

\(A=\frac{1}{1+2}+\frac{1}{1+2+3}+...+\frac{1}{1+2+3+...+100}\)

\(A=\frac{1}{3}+\frac{1}{6}+...+\frac{1}{5050}\)

\(A=2\left(\frac{1}{6}+\frac{1}{12}+...+\frac{1}{10100}\right)\)

\(A=2\left(\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{100.101}\right)=2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{100}-\frac{1}{101}\right)\)

\(A=2.\left(\frac{1}{2}-\frac{1}{101}\right)\)

Tự tính 

  \(A=\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{1}{5050}\)

    \(=2\left(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{10100}\right)\)

   \(=2\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{100.101}\right)\)

   \(=2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{100}-\frac{1}{101}\right)\)

    \(=2\left(\frac{1}{2}-\frac{1}{101}\right)\)

    \(=2.\frac{99}{202}\)

     \(=\frac{99}{101}\)

    M =1/1×2+1/2×3+1/3×4+............+1/99×100

=>M = 1/2 + 1/6 +1/12 +.....+1/9900

Ta có 1/2 = 1- 1/2

          1/6 = 1/2 - 1/3

          1/12 = 1/3 - 1/4

           ....

           1/9900 = 1/99 - 1/100

=> M = 1 - 1/2 +1/2 -1/3 +1/3 -1/4 + ..... + 1/98 - 1/99 +1/99 - 1/100

=> M = 1 - (1/2 +1/2 - 1/3 +1/3 -1/4+....+1/98 -1/99 +1/99) - 1/100

=> M = 1 - 0 - 1/100

=>  M = 1-1/100

=>  M = 99/100

Vậy M =99/100

M=2-1/1x2+3-2/2x3+...+100-99/99x100

M=1-1/2+1/2-1/3+1/3-1/4+...+1/99-1/100

M=1-1/100

M=99/100

Vậy giá trị của M bằng 99/100(0,99)

\(\frac{1}{3}-\frac{3}{4}-\frac{-3}{5}+\frac{1}{72}-\frac{2}{9}-\frac{1}{36}+\frac{1}{15}\)

\(=\left\{\frac{1}{3}+\frac{3}{5}+\frac{1}{15}\right\}\)\(-\left\{\frac{3}{4}+\frac{2}{9}+\frac{1}{36}\right\}\)\(+\frac{1}{72}\)

\(=1-1+1+\frac{1}{72}\)

\(=\frac{1}{72}\)

Bạn nhờ mik giúp thì phải nhớ tíck mik đó

A=1/3-3/4-(-3/5)+1/72-2/9-1/36+1/15

A=(1/3+3/5+1/15)-(3/4+2/9+1/36)+1/72

A=1-1+1+1/72=1/72

k mình nha

C = 59/10 : 3/2 - ( 5/3 x 9/2 x 14/3) : 7/4

= 59/15 - 35 : 7/4

= 59/15 - 20

= -241/15

\(4\cdot\left(-\dfrac{1}{2}\right)^{^3}+2\cdot\left(-\dfrac{1}{2}\right)^{^2}+3\cdot\left(-\dfrac{1}{2}\right)+1=\left(-\dfrac{1}{2}\right)\left[4\cdot\left(-\dfrac{1}{2}\right)^{^2}+2\left(-\dfrac{1}{2}\right)+3\right]+1=\left(-\dfrac{1}{2}\right)\left(4\cdot\dfrac{1}{4}-1+3\right)+1=\left(-\dfrac{1}{2}\right)\left(1-1+3\right)+1=3\left(-\dfrac{1}{2}\right)+1=-\dfrac{3}{2}+1=-\dfrac{1}{2}\)