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a) 7/4 + 3/2 + ( - 9/16 ) = 13/4 + ( -9/16 ) = 41/112
b) - 2/7 + 3/5 + 9/7 + ( -18/5 )= ( - 2/7 + 9/7 ) + [( 3/5 + ( - 18/5 )] = 1 + ( - 3/1 ) = - 2/1
< tách ra ik >
a) 7/4 + 3/2 + ( - 9/16 ) = 13/4 + ( -9/16 ) = 41/112
b) - 2/7 + 3/5 + 9/7 + ( -18/5 )= ( - 2/7 + 9/7 ) + [( 3/5 + ( - 18/5 )] = 1 + ( - 3/1 ) = - 2/1
< tách ra ik >
\(S=\frac{1}{1}-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{40}-\frac{1}{43}+\frac{1}{43}-\frac{1}{46}\)
\(\Rightarrow S=1-\frac{1}{46}\)
\(\Rightarrow S=\frac{46}{46}-\frac{1}{46}\)
\(\Rightarrow S=\frac{45}{46}\)
Nhớ k cho mình nhé
Thi tốt nhé bạn
S=1-1/4+1/4-1/7+..........+1/43-1/46
S=1-1/46
S=45/46
mk lm tắt bước nha nhưng đúng đó
\(a,3x+17=-5\\ \Rightarrow3x=-22\\ \Rightarrow x=-\dfrac{22}{3}\\ b,\dfrac{-5}{8}=\dfrac{x}{16}\\ \Rightarrow x=\dfrac{-5}{8}.16\\ \Rightarrow x=-10\\ c,\dfrac{4}{9}+\dfrac{7}{3}:x=\dfrac{1}{5}\\ \Rightarrow\dfrac{7}{3}:x=-\dfrac{11}{45}\\ \Rightarrow x=-\dfrac{105}{11}\)
\(a)3.x+17=-5\)
\(3.x\) \(=\left(-5\right)-170=-22\)
\(x\) \(=\left(-22\right)\div3\)
\(x\) \(=\dfrac{-22}{3}\)
\(b)\dfrac{-5}{8}=\dfrac{x}{16}\)
\(\Rightarrow x=\dfrac{\left(-5\right)\times16}{8}=\dfrac{-80}{8}=-10\)
\(c)\dfrac{4}{9}+\dfrac{7}{3}:x=\dfrac{1}{5}\)
\(\dfrac{7}{3}:x=\dfrac{1}{5}-\dfrac{4}{9}\)
\(\dfrac{7}{3}:x=\dfrac{1}{5}+\left(\dfrac{-4}{9}\right)=\dfrac{9}{45}+\left(\dfrac{-20}{45}\right)=\dfrac{-11}{45}\)
\(x=\dfrac{7}{3}:\left(\dfrac{-11}{45}\right)=\dfrac{7}{3}\times\left(\dfrac{-45}{11}\right)\)
\(x=\dfrac{-315}{33}=\dfrac{-105}{11}\)
\(=\dfrac{7}{10}.\dfrac{8}{3}.20.\dfrac{3}{8}.\dfrac{5}{28}=\dfrac{5}{2}\)
\(\Leftrightarrow\dfrac{x}{-4}=\dfrac{21}{y}=\dfrac{z}{-80}=\dfrac{3}{4}\)
=>x=-3; y=28; z=-60
a) - 18 ; - 12 ; - 7 ; 0 ; 3 ; 21 ; 33
b) - 101 ; - 22 ; - 19 ; - 2 ; 0 ; 20 ; 27 ; 33.
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