a) Tính tổng: \(S=\left(\frac{-1}{7}\right)^0+\left(\frac{-1}{7}\right)^1+\left(\frac{-1}{7}\right)^2+...+\left(\frac{-1}{7}\right)^{2007}\)
b) Chứng minh rằng : \(\frac{1}{2!}+\frac{2}{3!}+\frac{3}{4!}+...+\frac{99}{100!}
a) Tính \(S=\left(-\frac{1}{7}\right)^0+\left(-\frac{1}{7}\right)^1+\left(-\frac{1}{7}\right)^2+...+\left(-\frac{1}{7}\right)^{2007}\)
b) Chứng Minh : \(\frac{1}{2!}+\frac{2}{3!}+\frac{3}{4!}+...+\frac{99}{100!}<1\)
tính tổng \(S=\left(-\frac{1}{7}\right)^0+\left(-\frac{1}{7}\right)^1+\left(-\frac{1}{7}\right)^3+\left(-\frac{1}{7}\right)^4+.....+\left(-\frac{1}{7}\right)^{2007}\)
S=1-1/7-(1/7)^3-......-(1/7)^2017
49S=49-7-1/7-(1/7)^3-.,.....-(1/7)^2015
49S-S=48S=49-7-1-(1/7)^2017
48S=41-(1/7)^2017
S=41/48-(1/7)^2017/48
k nha
Tính tổng: S= \(\left(-\frac{1}{7}\right)^0+\left(-\frac{1}{7}\right)^1+\left(-\frac{1}{7}\right)^2+...+\left(-\frac{1}{7}\right)^{2007}\)
S=1+(-1/7)^1+(-1/7)^2+...+(-1/7)^2007
=>7S=7+(-1/7)^1+(1/7)^2+...+(-1/7)^2006
=>(7-1)S=6-(1/7)^2007
=>S=1-(-1/7^2007/6)
1/7S=(-1/7)^1+...+(-1/7)2018
1/7S-S=(-1/7)^1+....+(-1/7)^2018-(-1/7)^0-...-(-1/7)^2017
-6/7S=(-1/7)^2018-1=(-1/7)^2018-1:-6/7
Nguyễn Huy Thắng giải giúp mjnk bài này vs
tính tổng S=\(\left(\frac{-1}{7}\right)^0+\left(\frac{-1}{7}\right)^1+\left(\frac{-1}{7}\right)^2+...+\left(\frac{-1}{7}\right)^{2007}\)
S=(−1/7)^0+(−1/7)^1+(−1/7)^2+...+(−1/7)^2007
7S = 1+(−1/7)^1+(−1/7)^2+...+(−1/7)^2007
=> 7S = 7+(−1/7)^1+(−1/7)^2+...+(−1/7)^2006
=> 6S = 6-(−1/7)^2007
=> S= 1-(−1/7^2007/6)
Bài 1:
a, Cho S=\(\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+...+\frac{1}{9^2}\) .Chứng minh rằng \(\frac{2}{5}< S< \frac{8}{9}\)
b, Tìm x thuộc z để phân số \(\frac{x^2-5x-1}{x+2}\)có giá trị là số nguyên
c, Chứng minh rằng \(\left(\frac{7}{65}+1\right)\left(\frac{7}{84}+1\right)\left(\frac{7}{105}+1\right)\left(\frac{7}{124}+1\right)...\left(\frac{7}{153+1}\right)\left(\frac{7}{560}+1\right)< 2\)
d, Chứng minh rằng \(\frac{1}{3}-\frac{2}{3^2}+\frac{3}{3^3}-\frac{4}{3^4}+\frac{5}{3^5}-...+\frac{99}{3^{99}}-\frac{100}{3^{100}}< \frac{3}{16}\)
\(Tính.S=\left(-\frac{1}{7}\right)^0+\left(-\frac{1}{7}\right)^1+\left(-\frac{1}{7}\right)^2+...+\left(-\frac{1}{7}\right)^{2007}\)
\(CMR.\frac{1}{2!}+\frac{2}{3!}+\frac{3}{4!}+...+\frac{99}{100!}< 1\)
Tính gọn tổng sau :
a) \(S=\left(-\frac{1}{7}\right)^0+\left(-\frac{1}{7}\right)^1+\left(-\frac{1}{7}\right)^2+...\left(-\frac{1}{7}\right)^{2007}\)
b)\(Q=\frac{3}{2^3}+\frac{4}{2^4}+\frac{5}{2^5}+...+\frac{100}{2^{100}}\)
giúp mình nha các bạn, cam on nhìu
Bài 1 Thưc hiện phép tính ( tính nhanh nếu có thể)
a)\(\frac{-1}{24}-\left[\frac{1}{4}-\left(\frac{1}{2}-\frac{7}{8}\right)\right]\)
b)\(\left(\frac{5}{7}-\frac{7}{5}\right)-\left[\frac{1}{2}-\left(\frac{-2}{7}-\frac{1}{10}\right)\right]\)
C)\(\left(\frac{-1}{2}\right)-\left(\frac{-3}{5}\right)+\left(\frac{-1}{9}\right)+\frac{1}{17}-\left(\frac{-2}{7}\right)+\frac{4}{35}-\frac{7}{18}\)
d)\(\left(3-\frac{1}{4}+\frac{2}{3}\right)-\left(5-\frac{1}{3}-\frac{6}{5}\right)-\left(6-\frac{7}{4}+\frac{3}{2}\right)\)
Bài 1 :a, Tính tổng\(S=\left(-\frac{1}{7}\right)^0+\left(-\frac{1}{7}\right)^1+\left(-\frac{1}{7}\right)^2+.......+\left(-\frac{1}{7}\right)^{2007}\)
b, CMR \(\frac{1}{2!}+\frac{2}{3!}+\frac{3}{4!}+.......+\frac{99}{100!}<1\)
c, CMR: mọi số nguyên dương n thì: \(3^{n+2}-2^{n+2}+3^n-2^n\)chia hết cho 10
3n+2 - 2n+2 +3n - 2n = 3n . 32 - 2n. 22 +3n -2n
= 3n(32+1) - (2n.22 +2n)
=3n . 10 - 2n .5
=3n.10 - 2n-1 .2 .5
= 3n.10 - 2n-1 .10
= 10(3n - 2n-1)
vì 10 chia hết cho 10 nên 10(3n-2n-1) chia hết cho 10
=> 3n+2 - 2n+2 +3n -2n chia hết cho 10
Ai làm nhanh nhất mình sẽ **** xin cảm ơn các bạn mình đang cần gấp