Rút gọn A= 1 + 5 + 5^2 + 5^ 3 + ... + 5^ 100
rút gọn
a)1+5+5^2+5^3+...+5^300
b)1+3+3^2+3^3+...+3^100
a) Rút gọn tổng A = 20 + 21 + 22 + 23 + .... 250
b) Rút gọn tổng B = 5 + 52 + 53 +..... +599+ 5100
c) Rút gọn tổng C = 3 - 32 + 33 - 34 .....+ 32007 - 32008 + 32009 - 32010
d) Rút gọn tổng S100 = 5 + 5 x 9 + 5 x 92 + 5 x 93+ ......5 x 999
\(A=2^0+2^1+2^2\)\(+2^3+...+\)\(2^{50}\)
\(2A=2+2^2+2^3+...+2^{51}\)
\(2A-A=A=2^{51}-2^0\)
\(B=5+5^2+5^3+...+5^{99}+5^{100}\)
\(5B=5^2+5^3+5^4+...+5^{100}+5^{101}\)
\(5B-B=4B=5^{101}-5\)
\(B=\frac{5^{101}-5}{4}\)
\(C=3-3^2+3^3-3^4+...+\)\(3^{2007}-3^{2008}+3^{2009}-3^{2010}\)
\(3C=3^2-3^3+3^4-3^5+...-3^{2008}+3^{2009}-3^{2010}+3^{2011}\)
\(3C+C=4C=3^{2011}+3\)
\(C=\frac{3^{2011}+3}{4}\)
\(S_{100}=5+5\times9+5\times9^2+5\times9^3+...+5\times9^{99}\)
\(S_{100}=5\times\left(1+9+9^2+9^3+...+9^{99}\right)\)
\(9S_{100}=5\times\left(9+9^2+9^3+...+9^{99}+9^{100}\right)\)
\(9S_{100}-S_{100}=8S_{100}=5\times\left(9^{100}-1\right)\)
\(S_{100}=\frac{5\times\left(9^{100}-1\right)}{8}\)
Rút gọn tổng sau
A=1+2+2^2+2^3+...+2^50+2^51
Cho B=5+5^2+5^3+...+5^99+5^100
\(A=1+2+2^2+...+2^{51}\)
\(2A=2+2^2+2^3+...+2^{52}\)
\(2A-A=\left(2+2^2+2^3+...+2^{52}\right)-\left(1+2+2^2+...+2^{51}\right)\)
\(A=2^{52}-1\)
\(B=5+5^2+5^3+...+5^{100}\)
\(5B=5^2+5^3+5^4+...+5^{101}\)
\(5B-B=\left(5^2+5^3+5^4+...+5^{101}\right)-\left(5+5^2+5^3+...+5^{100}\right)\)
\(4B=5^{101}-5\)
\(B=\frac{5^{101}-5}{4}\)
Rút gọn
A=1*4/2*3+2*5/3*4+3*6/4*5+.........+98*101/99*100
a) Rút gọn biểu thức sau:
A=2*2^2+3*2^3+4*2^4+5*2^5+...+100*2^100
b) Cho B=1/2-1/3+1/4-1/5+...+1/98-1/99
CMR: 0,2< B < 0,4
Rút gọn
A = 1+2^2+.............2^100
B=5^1+5^2+.....................5^199
A=1+2^2+...+2^100
2A=2+2^2+2^3+...+2^101
2A=2^101-1
A=(2^101-1):2
\(B=5^1+5^2+...+5^{199}\)
\(\Rightarrow5B=5^2+5^3+...+5^{200}\)
\(\Rightarrow5B-B=\left(5^2+5^3+...+5^{200}\right)-\left(5^1+5^2+...+5^{199}\right)\)
\(\Rightarrow4B=5^{200}-5\)
\(\Rightarrow B=\frac{5^{200}-5}{4}\)
Bài 10: Rút gọn
A = 1+5+5^2+......+5^100
A=1+5+52+...+5100
=>5A=5+52+53+...+5101
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A=1+5+52+....5100
___________________________________
4A=5101-1
=>A=5101-1/4
5A=5+5^2+5^3+.....+5^101
5A-A=5^101-1
A=\(\frac{5^{101}-1}{4}\)
Rút gọn
A=1+2+22+23+.......+2100
B=5+52+53+.........+52016
Lm A ví dụ trước nha :
\(A=1+2+2^2+2^3+....+2^{100}\)
\(\Rightarrow2A=2+2^2+....+2^{101}\)
\(\Rightarrow A=2A-A=2^{101}-1\)
\(A=1+2+2^2+...+2^{100}\)
\(\Rightarrow2A=2+2^2+2^3+...+2^{101}\)
\(\Rightarrow2A-A=2^{101}-1\)
\(\Rightarrow A=2^{101}-1\)
\(B=5+5^2+5^3+...+5^{2016}\)
\(\Rightarrow5B=5^2+5^3+5^4+...+5^{2017}\)
\(\Rightarrow5B-B=5^{2017}-5\)
\(\Rightarrow4B=5^{2017}-5\)
\(\Rightarrow B=\frac{5^{2017}-5}{4}\)
Các bạn giúp mình bài này với:
Rút gọn: a = 1 + 3/2^3 + 4/2^4 + 5/2^5 + ... + 100/2^100
Cảm ơn các bạn. :)