Tính hợp lý nhất
a, 1/210+1/240+1/272+1/306
b, 191/210+161/240+129/272+95/306
giúp mình với huhuhu
1/210+1/240+1/272+1/306
1/210+1/240+1/272+1/306
1/210+1/240+1/272+1/306
Chứng minh rằng\(A = {1 \over 101}+{1\over 102} +{1\over 103}+{1\over 104}+...+{1\over 200}>{7\over 12}\)
1.
\(A = {3 \over 5}.{2017 \over 2016} - {3 \over 5}- {1 \over 2016} + {2 \over 5}\)
\(B = ({12 \over 199}+ {23 \over 200} - {34 \over 201}).({1\over 2} - {1 \over 3}-{1 \over 6})\)
\(C= 2{1 \over 3}+{11 \over 5}: 33-{1 \over 50}.\)(-5)2
\(D = {4^5 . 9^4 - 10 . 6^9 \over 2^10 . 3^8 + 6^8 . 28}\)
E =( -1).(-1)2.(-1)3.(-1)4......(-1)2014
2.
\(A= {5\over2.4} + {5\over4.6} + {5\over6.8} + .....+ {5\over48.50}\)
\(B={1\over3.6} + {1\over6.9} + {1\over9.12} +.....+{1\over30.33}\)
CMR: \((1+{1 \over 2})(1+{1 \over 2^2})(1+{1 \over 2^3})...(1+{1 \over 2^{2020}})<3\)
anh chị giúp em nhé
\(x = {{2.1.2+1} \over 1.2}+{{2.2.3+1} \over 2.3}+ {{2.3.4+1} \over 3.4}+{{2.4.5+1} \over 4.5}+...+{{2.9.10+1} \over 9.10}\)
\({1 \over x} + {1 \over y} + {1 \over xy} = {2 \over 3}\)
Tìm cặp số nguyên x, y