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a, 10+15+20+....+295+x.300+x=67
10+15+20+...+295+x(300+1)=67
10+15+20+...+295+x.301=67
8845+x.301=67
67-8845=x.301
-8878=x.301
x=-29/149/301
b,
\(\frac{1}{7.6}+\frac{1}{6.5}+\frac{1}{5.4}+\frac{1}{4.3}+\frac{1}{3.2}+\frac{1}{2.1}-\frac{1}{x+1}=\frac{59}{77}\)
\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}-\frac{1}{x+1}=\frac{59}{77}\)
\(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}-\frac{1}{x+1}=\frac{59}{77}\)\(1-\frac{1}{7}-\frac{1}{x+1}=\frac{59}{77}\)
\(\frac{6}{7}-\frac{1}{x+1}=\frac{59}{77}\)
\(\frac{1}{x+1}=\frac{6}{7}-\frac{59}{77}\)
\(\frac{1}{x+1}=\frac{1}{11}\)
suy ra x+1=11
suy ra x=10
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a)
\(\frac{-2}{-15}-x=\frac{-3}{10}\)
\(x=\frac{4}{30}+\frac{9}{30}\)
\(x=\frac{13}{30}\)
b)
\(x-\frac{1}{15}=\frac{1}{10}\)
\(x=\frac{3}{30}+\frac{2}{30}\)
\(x=\frac{5}{30}=\frac{1}{6}\)
c)
\(\frac{-3}{8}-x=\frac{5}{12}\)
\(x=\frac{-9}{24}-\frac{10}{24}\)
\(x=\frac{-19}{24}\)
Giúp đõ mk vs nha! THANKS
\(\Leftrightarrow\left(x,y-3\right)\in\left\{\left(1;-12\right);\left(-12;1\right);\left(2;-6\right);\left(-6;2\right);\left(3;-4\right);\left(-4;3\right);\left(4;-3\right);\left(-3;4\right);\left(6;-2\right);\left(-2;6\right);\left(12;-1\right);\left(-1;12\right)\right\}\)
hay \(\left(x,y\right)\in\left\{\left(1;-9\right);\left(-12;4\right);\left(2;-3\right);\left(-6;5\right);\left(3;-1\right);\left(-4;6\right);\left(4;0\right);\left(-3;7\right);\left(6;1\right);\left(-2;9\right);\left(12;2\right);\left(-1;15\right)\right\}\)
\(\dfrac{3}{x+5}=15\%\)
\(\dfrac{3}{x+5}=\dfrac{3}{20}\)
\(\Leftrightarrow x+5=20\)
\(x=20-5\)
\(x=15\)
Lời giải:
\(\dfrac{3}{x+5}=15\%\)
\(\Rightarrow\dfrac{3}{x+5}=\dfrac{3}{20}\)
\(\Rightarrow x+5=20\)
\(\Rightarrow x=15\)