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a) \(x:2,4=3,5:0,7\)
=> \(x:2,4=5\)
=> \(x=5.2,4\)
=> \(x=12\)
Vậy \(x=12.\)
b) \(2\frac{1}{5}:x=-3\frac{1}{4}:\left(-2\frac{2}{5}\right)\)
=> \(\frac{11}{5}:x=-\frac{13}{4}:\left(-\frac{12}{5}\right)\)
=> \(\frac{11}{5}:x=\frac{65}{48}\)
=> \(x=\frac{11}{5}:\frac{65}{48}\)
=> \(x=\frac{528}{325}\)
Vậy \(x=\frac{528}{325}.\)
c) \(4,8:0,16=x:0,4\)
=> \(30=x:0,4\)
=> \(x=30.0,4\)
=> \(x=12\)
Vậy \(x=12.\)
Chúc bạn học tốt!
\( a)x:2,4 = 3,5:0,7\\ \Leftrightarrow x:2,4 = 5\\ \Leftrightarrow x = 5 \times 2,4\\ \Leftrightarrow x = 12\\ b)2\dfrac{1}{5}:x = - 3\dfrac{1}{4}:\left( { - 2\dfrac{2}{5}} \right)\\ \Leftrightarrow \dfrac{{11}}{5}:x = \dfrac{{ - 13}}{4}:\dfrac{{ - 12}}{5}\\ \Leftrightarrow \dfrac{{11}}{5}:x = \dfrac{{65}}{{48}}\\ \Leftrightarrow x = \dfrac{{11}}{5}:\dfrac{{65}}{{48}}\\ \Leftrightarrow x = \dfrac{{528}}{{325}}\\ c)4,8:0,16 = x:0,4\\ \Leftrightarrow 30 = x:0,4\\ \Leftrightarrow x = 30 \times 0,4\\ \Leftrightarrow x = 12 \)
\(\frac{125}{\left(-5\right)^n}=-25\Rightarrow\left(-5\right)^n=\frac{125}{-25}=-5\)
\(\Rightarrow\left(-5\right)^n=\left(-5\right)^1\)
\(\Rightarrow n=1\)
a) \(\frac{125}{\left(-5\right)^n}=-25\)
⇒ \(\left(-5\right)^n=125:\left(-25\right)\)
⇒ \(\left(-5\right)^n=-5\)
⇒ \(\left(-5\right)^n=\left(-5\right)^1\)
⇒ \(n=1\)
Vậy \(n=1.\)
Chúc bạn học tốt!
\(f\left(x\right)=x^2-2\)
a) Thay \(x=-1\) vào \(f\left(x\right)\) ta được:
\(f\left(-1\right)=\left(-1\right)^2-2\)
\(f\left(-1\right)=1-2\)
\(f\left(-1\right)=-1.\)
+ Thay \(x=\frac{2}{3}\) vào \(f\left(x\right)\) ta được:
\(f\left(\frac{2}{3}\right)=\left(\frac{2}{3}\right)^2-2\)
\(f\left(\frac{2}{3}\right)=\frac{4}{9}-2\)
\(f\left(\frac{2}{3}\right)=-\frac{14}{9}.\)
b) Ta có: \(y=x^2-2\)
Với \(y=7\) ta được:
\(7=x^2-2\)
\(\Rightarrow x^2=7+2\)
\(\Rightarrow x^2=9\)
\(\Rightarrow\left[{}\begin{matrix}x=3\\x=-3\end{matrix}\right.\)
Vậy với \(y=7\) thì \(x\in\left\{3;-3\right\}.\)
Chúc bạn học tốt!
\(\left(\frac{1}{4}-x\right)\left(x+\frac{2}{5}\right)=0\)
Ta xét 2 trường hợp
\(\begin{cases}\frac{1}{4}-x=0\\x+\frac{2}{5}=0\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{1}{4}\\x=-\frac{2}{5}\end{cases}}\)
tớ mới làm bài 1 thôi bài 2 3 tớ ko có thời gian
\(=\frac{16}{5}.\frac{15}{16}-\left(\frac{3}{4}+\frac{2}{7}\right):\left(\frac{-29}{28}\right)\)
\(=3-\left(\frac{21}{28}+\frac{8}{28}\right):\left(\frac{-29}{28}\right)\)
\(=3-\left(\frac{29}{28}\right).\left(\frac{-28}{29}\right)\)
\(=3-\left(-1\right)\)
\(=4\)
b) \(=\left(\frac{1}{4}+\frac{25}{2}-\frac{5}{16}\right):\left(12-\frac{7}{12}:\left(\frac{3}{8}-\frac{1}{12}\right)\right)\)
\(=\left(\frac{4}{16}+\frac{200}{16}-\frac{5}{16}\right):\left(12-\frac{7}{12}:\left(\frac{3.3}{2.3.4}-\frac{2}{2.3.4}\right)\right)\)
\(=\left(\frac{199}{16}\right):\left(12-\frac{7}{12}:\left(\frac{9}{24}-\frac{2}{24}\right)\right)\)
\(=\frac{199}{16}:\left(12-\frac{7}{12}.\frac{24}{7}\right)\)
\(=\frac{199}{16}:\left(12-2\right)\)
\(=\frac{199}{16}:10\)
\(=\frac{199}{160}\)
c) \(\left(\frac{-3}{5}+\frac{5}{11}\right):\frac{-3}{7}+\left(\frac{-2}{5}+\frac{6}{5}\right):\frac{-3}{7}\)
\(\left(\frac{-33}{55}+\frac{25}{55}\right):\frac{-3}{7}+\left(\frac{4}{5}\right):\frac{-3}{7}\)
\(\left(\frac{-8}{55}\right).\frac{-7}{3}+\frac{4}{5}.\frac{-7}{3}\)
\(\frac{-7}{3}\left(\frac{-8}{55}+\frac{4}{5}\right)\)
\(\frac{-7}{3}.\frac{36}{55}=\frac{-84}{55}\)
1)
b) \(\frac{5}{2}+\frac{2}{3}.\left(-\frac{3}{4}\right)\)
\(=\frac{5}{2}+\left(-\frac{1}{2}\right)\)
\(=2.\)
2)
\(\frac{9}{1,2}=\frac{-30}{x}\)
⇒ \(9.x=\left(-30\right).1,2\)
⇒ \(9.x=-36\)
⇒ \(x=\left(-36\right):9\)
⇒ \(x=-4\)
Vậy \(x=-4.\)
Chúc bạn học tốt!