Đặt A \(=\) \(\frac{1}{3}+\frac{2}{3^2}+...+\frac{100}{3^{100}}\)
=> 3A\(=1+\frac{2}{3}+\frac{3}{3^2}+...+\frac{100}{3^{99}}\)
=> 3A- A \(=\) 2A \(=1+\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+...+\frac{1}{3^{99}}-\frac{100}{3^{100}}\)
Đặt B \(=1+\frac{1}{3}+\frac{1}{3^2}+...+\frac{1}{3^{99}}\)=>\(3B=3+1+\frac{1}{3^2}+\frac{1}{3^3}+...+\frac{1}{3^{98}}\)
=> 2B \(=3-\frac{1}{3^{99}}
Chứng minh rằng:
A = 1/3 + 1/32 + 1/33 + ..........+ 1/399 < 1/2
B = 3/12x 22 + 5/22 x 32 + 7/32 x 42 +............+ 19/92 x 102 < 1
C = 1/3 + 2/32 + 3/33 + 4/34 +.........+ 100/3100 ≤ 0
Chứng minh rằng: a, 1/12.22+5/22.32+5/32.42+...+5/92.102 <1 b,1/3+2/32+3/33+...+100/3100 <3/4
chứng minh rằng: 1/3 + 1/3 mũ 2 + 1/3 mũ 3 + ... + 1/3 mũ 2021<1/2
chứng minh rằng: 1/3 + 1/3 mũ 2 + 1/3 mũ 3 + ... + 1/3 mũ 2021
Chứng minh rằng tổng \(P=\frac{1}{3^2}-\frac{1}{3^4}+...+\frac{1}{3^{2006}}-\frac{1}{3^{2008}}\) nhỏ hơn 0, 1
Chứng minh rằng 2/3^2+3/3^3+4/3^4+..................+2016/3^2016< 5/12
Chứng minh rằng: (3^n+3) +(2^n+3) +(3^n+1) + (2^n+2) chia hết cho 6
Chứng minh rằng |x+1|+|x+3|+|x+5| ≥ 4.
Mk đg cần gấp. TKS mn
