S=2+4+6+...+98+100

S=\(\frac{\left[\left(\frac{100-2}{2}+1\right).\left(100+2\right)\right]}{2}=2550\)

S=1+2+3+4+...+2016+2017

S=\(\frac{\left(2017-1+1\right).\left(2017+1\right)}{2}=2035153\)

1.Số lượng số của S= (2017-1)+1=2017 số

tổng=(2016+1).(2016:2)+2017=2 035 153

2.Số lượng số của S=(100-2):2+1=50 số

tổng=(100+2).(50:2)=2 550

LỚP 6 ĐÂY HẢ BN

có ai pik làm ko

cs tui bt

t

\(S=1+9+9^2+.....+9^{2017}\)

\(9S=9+9^2+9^3+.....+9^{2017}+9^{2018}\)

\(9S-S=8S=9^{2018}-1\)

\(S=\frac{9^{2018}-1}{8}\)

\(S=1+9+9^2+...+9^{2017}\)

\(\Rightarrow9S=9+9^2+9^3+...+9^{2018}\)

\(\Rightarrow9S-S=8S=\left(9+9^2+9^3+...+9^{2018}\right)-\left(1+9+9^2+...+9^{2017}\right)\)

\(8S=9^{2018}-1\)

\(\Rightarrow S=\frac{9^{2018}-1}{8}\)

\(S=3+\frac{3}{2}+\frac{3}{2^2}+....+\frac{3}{2^9}\)

\(S\cdot\frac{1}{3}=1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^9}\)

\(S\cdot\frac{2}{3}=2+1+\frac{1}{2}+...+\frac{1}{2^8}\)

\(S\cdot\frac{2}{3}-S\cdot\frac{1}{3}=2+1+\frac{1}{2}+...+\frac{1}{2^8}-1-\frac{1}{2}-...-\frac{1}{2^9}\)

\(S\cdot\frac{1}{3}=2-\frac{1}{2^9}\)

\(S=\left(2-\frac{1}{2^9}\right):\frac{1}{3}\)

\(S=\left(2-\frac{1}{2^9}\right)\cdot3\)

\(S=6-\frac{3}{2^9}\)

\(S=\frac{6\cdot2^9-3}{2^9}\)

\(S=1+9+9^2+....+9^{2017}\)

\(9S=9.\left(1+9+9^2+...+9^{2017}\right)\)

\(9S=9+9^2+9^3+...+9^{2018}\)

\(8S=9S-S=\left(9+9^2+9^3+...+9^{2018}\right)-\left(1+9+9^2+....+9^{2017}\right)\)

\(8S=9^{2018}-1\)

\(S=\left(9^{2018}-1\right)\div8=\frac{9^{2018}-1}{8}\)

Vậy S = \(\frac{9^{2018}-1}{8}\)

S = 1 + 9 + 9\(^2\)+ . . . + 9\(^{2017}\)

9S = 9 + 9\(^2\)+ 9\(^3\)+ . . . + 9\(^{2018}\)

S = [ 9 + 9\(^2\)+ 9\(^3\)+ . . . + 9\(^{2018}\)] - [ 1 + 9 + 9\(^2\)+ . . . + 9\(^{2017}\)

S = [ 9 - 9 ] + [ 9\(^2\)- 9\(^2\) ] + [ 9\(^3\)- 9\(^3\)] + . . . + [ 9\(^{2017}\)- 9\(^{2017}\)] + [ 9\(^{2018}\)- 1 ]

S = 9\(^{2018}\)- 1

\(S=1+9+9^2+...+9^{2017}\)

\(\Rightarrow9S=9+9^2+9^3+...+9^{2018}\)

\(\Rightarrow9S-S=\left(9+9^2+...+9^{2018}\right)-\left(1+9+...+9^{2017}\right)\)

\(\Rightarrow8S=9^{2018}-1\)

\(\Rightarrow S=\frac{9^{2018}-1}{8}\)

      S=1+9+9²+9³+...+9²⁰¹⁷

9S    =(9⁰+9+9²+9³+...+9²⁰¹⁷).2

9S    =9+9²+9³+9⁴+...+9²⁰¹⁷+9²⁰¹⁸

9S-S =(9+9²+9³+9⁴+...+9²⁰¹⁷+9²⁰¹⁸)-(9⁰+9+9²+9³+...+9²⁰¹⁷)

8S    =9²⁰¹⁸-9⁰

S      =(9²⁰¹⁸-9⁰):8

bn có thể vào 1 số câu hỏi tương tự để tham khảo ( có thể giống dạng nhưng không giống số )

minh cung dang bi day