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b,\(\frac{2}{3}\)+\(\frac{1}{3}\).(\(\frac{-2}{3}\)+\(\frac{5}{6}\)):\(\frac{2}{3}\)
=\(\frac{2}{3}\)+\(\frac{1}{3}\).(\(\frac{-4}{6}\)+\(\frac{5}{6}\)):\(\frac{2}{3}\)
=\(\frac{2}{3}\)+\(\frac{1}{3}\).\(\frac{1}{6}\).\(\frac{3}{2}\)
=\(\frac{2}{3}\)+\(\frac{1}{18}\).\(\frac{3}{2}\)
=\(\frac{2}{3}\)+\(\frac{1}{6}\).\(\frac{1}{2}\)
=\(\frac{2}{3}\)+\(\frac{1}{12}\)
=\(\frac{8}{12}\)+\(\frac{1}{12}\)
=\(\frac{9}{12}\)=\(\frac{3}{4}\)
a; - \(\dfrac{10}{13}\) + \(\dfrac{5}{17}\) - \(\dfrac{3}{13}\) + \(\dfrac{12}{17}\) - \(\dfrac{11}{20}\)
= - (\(\dfrac{10}{13}\) + \(\dfrac{3}{13}\)) + (\(\dfrac{5}{17}\) + \(\dfrac{12}{17}\)) - \(\dfrac{11}{20}\)
= - 1 + 1 - \(\dfrac{11}{20}\)
= 0 - \(\dfrac{11}{20}\)
= - \(\dfrac{11}{20}\)
b; \(\dfrac{3}{4}\) + \(\dfrac{-5}{6}\) - \(\dfrac{11}{-12}\)
= \(\dfrac{9}{12}\) - \(\dfrac{10}{12}\) + \(\dfrac{11}{12}\)
= \(\dfrac{10}{12}\)
= \(\dfrac{5}{6}\)
c; [13.\(\dfrac{4}{9}\) + 2.\(\dfrac{1}{9}\)] - 3.\(\dfrac{4}{9}\)
= [\(\dfrac{52}{9}\) + \(\dfrac{2}{9}\)] - \(\dfrac{4}{3}\)
= \(\dfrac{54}{9}\) - \(\dfrac{4}{3}\)
= \(\dfrac{14}{3}\)
M=3/1.2-5/2.3+7/3.4-9/4.5+11/5.6-13/6.7+15/7.8+17/8.9
=(1/1.1+2/1.2)-(2/2.3+3/2.3)+(3/3.4+4/3.4)-(4/4.5+5/4.5)+...+(8/8.9+9/8.9)(phần ... là làm tương tự nhé)
=1/2+1-(1/3+1/2)+(1/4+1/3)-(1/5+1/4)+...+(1/9+1/8)(phần ... là làm tương tự nhé)
=1+(1/2-1/2)+(1/3-1/3)+(1/4-1/4)+...+(1/8-1/8)-1/9
=1+0+0+0+...+0-1/9
=1-1/9
=8/9
3.Tìm x biết:
a) \(2-x=17-\left(-5\right)\)
\(2-x=22\)
\(x=2-22\)
\(x=-20\)
Vậy \(x=-20\)
b) \(2x-6=-3-\left(-7\right)\)
\(2x-6=4\)
\(2x=6+4\)
\(2x=10\)
\(x=10:2\)
\(x=5\)
Vậy \(x=5\)
c) \(\left(3x-6\right).3=3^4\)
\(\left(3x-6\right).3=81\)
\(3x-6=81:3\)
\(3x-6=27\)
\(3x=27+6\)
\(3x=33\)
\(x=33:3\)
\(x=11\)
Vậy \(x=11\)
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a ) − 5 7 . 3 11 + − 5 7 . 8 11 + 5 7 = − 5 7 . 3 11 + 8 11 − 1 = 0
b ) 5 7 . 10 11 + 5 7 . 14 11 − 5 7 . 17 11 = 5 7 . 10 11 + 14 11 − 17 11 = 5 11
c ) − 52 57 d ) 4 3