a) \(\frac{a}{9}+\frac{3}{b}=\frac{1}{18}\Leftrightarrow\frac{ab+27}{9b}=\frac{1}{18}\left(1\right)\)
\(\Rightarrow9b=18\Rightarrow b=2\left(2\right)\)
Thay (2) vào (1) ta có
\(\frac{2a+27}{18}=\frac{1}{18}\Rightarrow2a+27=1\Rightarrow2a=-26\Rightarrow a=-13\)
tìm a, b thuộc Z
a) \(\frac{a}{9}--\frac{3}{b}=\frac{1}{18}\)
b) \(\frac{a}{4}-\frac{1}{6}=-\frac{b}{6}\)
1) tính:
a, ( \(\frac{17}{28}+\frac{18}{29}-\frac{19}{30}-\frac{20}{31}\) ).(\(\frac{-5}{12}+\frac{1}{4}+\frac{1}{6}\) )
b, \(\frac{\frac{7}{12}+\frac{5}{6}-1}{5-\frac{3}{4}+\frac{1}{3}}\)
2)Cho A=\(\frac{10n}{5n-3}\)
a) tìm n để A là số nguyên
b)tìm GTLN của A
tìm x biết :
a) \(\frac{6}{7}.x=\frac{18}{23}\)
b) \(2\frac{1}{2}.x=\frac{5}{6}\)
c) \(x:2\frac{3}{4}=9\frac{5}{8}\)
d)\(7\frac{1}{7}.\frac{1}{7}.x=22\frac{1}{8}\)
Cho A=\(\frac{1}{4}.\frac{3}{6}.\frac{5}{8}....\frac{43}{46}.\frac{45}{48}\) và B=\(\frac{2}{5}.\frac{4}{7}.\frac{6}{9}.....\frac{44}{47}.\frac{46}{49}\).So sánh A và B
1) Tính :
a) A = ( \(1-\frac{1}{2}\) ) + ( \(1-\frac{1}{4}\) ) + ( \(1-\frac{1}{8}\) ) + .......+ ( \(1-\frac{1}{512}\) ) + ( \(1-\frac{1}{1024}\) )
b) B = ( \(\frac{5^3}{6}+\frac{5^3}{12}+\frac{5^3}{20}+\frac{5^3}{42}+\frac{5^3}{56}+\frac{5^3}{72}+\frac{5^3}{90}\) ) : \(\frac{1124.2247-1123}{1124+1123.2247}\)
c) C = \(\frac{1}{3}+\frac{1}{9}+\frac{1}{18}+\frac{1}{30}+......+\frac{1}{14850}\)
Thực hiện phép tính:
A =\(\frac{5.\left(2^2.3^2\right)^9.\left(2^2\right)^6-2.\left(2^2.3\right)^{14}.3^4}{5.2^{28}.3^{18}-7.2^{29}.3^{18}}\)
B= \(81.\frac{12-\frac{12}{7}-\frac{12}{289}-\frac{12}{85}5+\frac{5}{13}+\frac{5}{169}+\frac{5}{91}}{4-\frac{4}{7}-\frac{4}{289}-\frac{4}{85}6+\frac{6}{13}+\frac{6}{169}+\frac{6}{91}}.\frac{158158158}{711711711}\)
Chứng minh rằng :
a) \(\frac{1}{2^2}+\frac{1}{4^2}+\frac{1}{6^2}+...+\frac{1}{100^2}< \frac{1}{2}\)
b) \(\frac{3}{4}+\frac{8}{9}+\frac{15}{16}+...+\frac{2499}{2500}>48\)
1) Tính:
a) \(\frac{\frac{1}{9}-\frac{5}{6}-4}{\frac{7}{12}-\frac{1}{36}-10}\)
b) \(\frac{\frac{15}{8}-\frac{15}{6}-\frac{15}{32}+\frac{15}{64}}{3-\frac{3}{2}-\frac{3}{4}+\frac{3}{8}}\)
1. tìm số nguyên x biết:
a)\(\left(\frac{1}{2}-\frac{1}{3}\right).6^x+6^{x+2}=6^{15}+6^{18}\)
b)\(\left(\frac{1}{2}-\frac{1}{6}\right).3^{x+4}-4.3^x=3^{16-4}.3^{13}\)
giúp mk nha
