B = 9 . [ 4/1.3.5+4/3.5.7+4/5.7.9+...+4/25.27.29]
B = 9 . [ 1/3-1/783]
= 9 . [ 1/3-1/783]
= 9 . 260/783=260/87<261/87<3
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Chứng minh B=36/1.3.5+36/3.5.7+36/5.7.9+...+36/25.27.29<3
Chứng minh rằng: B=36/1.3.5+36/3.5.7+36/5.7.9+...+36/25.27.29<3.
chứng minh rằng
\(B=\frac{36}{1.3.5}+\frac{36}{3.5.7}+\frac{36}{5.7.9}+...+\frac{36}{25.27.29}\)
Chứng minh B=\(\frac{36}{1.3.5}+\frac{36}{3.5.7}+\frac{36}{5.7.9}+...+\frac{36}{25.27.29}<3\)
1:a) Tính
\(A=\frac{36}{1.3.5}+\frac{36}{3.5.7}+\frac{36}{5.7.9}+...+\frac{36}{25.27.29}\)
b) CMR : A<3
\(\frac{36}{1.3.5}+\frac{36}{3.5.7}+\frac{36}{5.7.9}+... +\frac{36}{25.27.29}\)
Giúp mình bài này với nha!
G = 36/1.3.5 + 36/3.5.7 + 36/5.7.9 + ... + 36/25.27.29
tính G
Chứng minh rằng :
a) A=\(\frac{1}{1.2.3}+\frac{1}{2.3.4}+\frac{1}{3.4.5}+...+\frac{1}{18.19.20}<\frac{1}{4}\)
b) B=\(\frac{36}{1.3.5}+\frac{36}{3.5.7}+\frac{36}{5.7.9}+...+\frac{36}{25.27.29}<3\)
cho A=\(\frac{36}{1.3.5}+\frac{36}{2.5.7}+\frac{36}{5.7.9}+.....+\frac{36}{25.27.29}\) chứng minh A<3