mỗi p/số của A đều bé hơn 1/1.2+1/2.3+1/3.4+......+1/49.50
A<1-1/2+1/2-1/3+1/3-1/4+..........+1/49-1/50(tách ra thành hiệu)
A<1-1/50
mà 1/50>0=>1-1/50<1<2
A<1-1/50<1<2
A<2
chúc học tốt
CHO A=\(\frac{1}{1^2}+\frac{1}{2^2}+\frac{1}{3^2}+....+\frac{1}{50^2}\)
CHUNG MINH RANG A<2
Cho A=\(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{50}\)
Chung minh rang A khong co gia tri la mot so tu nhien
Mk dag can gap
chung minh rang A=\(\frac{1}{2}-\frac{2}{2^2}+\frac{3}{2^3}-\frac{4}{2^4}+...+\frac{99}{2^{99}}-\frac{100}{2^{100}}<\frac{2}{9}\)
a). Cho A=\(\frac{1}{2^2}\)+\(\frac{1}{3^2}\)+\(\frac{1}{4^2}\)+....+\(\frac{1}{2015^2}\).
Chung minh rang : A < 1.
b). Cho B=\(2^1\)+\(2^2\)+\(2^3\)+....+\(2^{2016}\).
Chung minh rang : B chia het cho 21.
2, chung minh rang
a, \(\frac{1}{2}-\frac{1}{4}+\frac{1}{8}-\frac{1}{16}+\frac{1}{32}-\frac{1}{64}<\frac{1}{3}\)
b,\(\frac{1}{3}-\frac{2}{^{3^2}}+\frac{3}{3^4}+........+\frac{99}{3^{99}}-\frac{100}{3^{100}}<\frac{3}{16}\)
chung minh rang \(\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+...+\frac{1}{100^2}\) <1
cho A=\(\frac{1}{1^2}+\frac{1}{2^2}+......+\frac{1}{50^2}\)Chưng minh rang a<2
giup mik voi
Cho A= \(\frac{1}{1^2}\)+ \(\frac{1}{2^2}\)+\(\frac{1}{3^2}\)+\(\frac{1}{4^2}\)+ ....+ \(\frac{1}{2018^2}\)
Chung to rang A < \(\frac{7}{4}\)minh dang can gap de nop cho thay
Cho A=\(\frac{1}{1^2}+\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+...+\frac{1}{50^2}\) Chứng minh A<2
