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a: =>x*2/15=2/7
=>x=2/7:2/15=2/7*15/2=15/7
b: x=3:7/5=15/7
c: x=-1/2:4/9=-1/2*9/4=-9/8
d: x=-8/3:3/8=-64/9
g: =>4/11x=2/5+1/3=6/15+5/15=11/15
=>x=11/15:4/11=121/60
l: =>1/4:x=1-3/2=-1/2
=>x=-1/4:1/2=-1/4*2=-1/2
k: =>x:7=-1/3+5/2=-2/6+15/6=13/6
=>x=91/6
a) \(\left(\dfrac{1}{2}x-3\right)\left(-\dfrac{1}{3}+x\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}\dfrac{1}{2}x-3=0\\-\dfrac{1}{3}+x=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\dfrac{1}{2}x=0+3\\-\dfrac{1}{3}+x=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=3:\dfrac{1}{2}\\x=0-\left(-\dfrac{1}{3}\right)\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=6\\x=\dfrac{1}{3}\end{matrix}\right.\)
d) \(9x^2=1\)
\(\Leftrightarrow x^2=1:9\)
\(\Leftrightarrow x^2=\dfrac{1}{9}\)
\(\Leftrightarrow x^2=\left(\dfrac{1}{3}\right)^2\)
\(\Leftrightarrow x=\dfrac{1}{3}\)
1. Tìm \(x\):
a) \(\dfrac{x}{5}=\dfrac{5}{6}+\dfrac{-19}{30}\)
\(\dfrac{x}{5}=\dfrac{1}{5}\)
\(\Rightarrow x=1\)
b) \(\dfrac{-5}{6}-x=\dfrac{7}{12}-\dfrac{1}{3}.x\)
\(\dfrac{-5}{6}-\dfrac{7}{12}=x-\dfrac{1}{3}.x\)
\(x-\dfrac{1}{3}.x=\dfrac{-17}{12}\)
\(\dfrac{2}{3}.x=\dfrac{-17}{12}\)
\(x=\dfrac{-17}{12}:\dfrac{2}{3}\)
\(x=\dfrac{-17}{8}\)
c) \(2016^3.2016^x=2016^8\)
\(2016^x=2016^8:2016^3\)
\(2016^x=2016^{8-3}\)
\(2016^x=2016^5\)
\(\Rightarrow x=5\)
d) \(\left(x+\dfrac{3}{4}\right):\dfrac{5}{2}=3\dfrac{1}{2}\)
\(\left(x+\dfrac{3}{4}\right):\dfrac{5}{2}=\dfrac{7}{2}\)
\(\left(x+\dfrac{3}{4}\right)=\dfrac{7}{2}.\dfrac{5}{2}\)
\(x+\dfrac{3}{4}=\dfrac{35}{4}\)
\(x=\dfrac{35}{4}-\dfrac{3}{4}\)
\(x=\dfrac{32}{4}=8\)
e) \(\left(2,8.x-2^5\right):\dfrac{2}{3}=3^2\)
\(\left(2,8.x-2^5\right)=9.\dfrac{2}{3}\)
\(2,8.x-2^5=6\)
\(2,8.x=6+32\)
\(2,8.x=38\)
\(x=38:2,8\)
\(x=\dfrac{95}{7}\)
f) \(\dfrac{4}{7}.x-\dfrac{2}{3}=\dfrac{2}{5}\)
\(\dfrac{4}{7}.x=\dfrac{2}{5}+\dfrac{2}{3}\)
\(\dfrac{4}{7}.x=\dfrac{16}{15}\)
\(x=\dfrac{16}{15}:\dfrac{4}{7}\)
\(x=\dfrac{28}{15}\)
g) \(\left(\dfrac{3x}{7}+1\right):\left(-4\right)=\dfrac{-1}{28}\)
\(\left(\dfrac{3x}{7}+1\right)=\dfrac{-1}{28}.\left(-4\right)\)
\(\dfrac{3x}{7}+1=\dfrac{1}{7}\)
\(\dfrac{3x}{7}=\dfrac{1}{7}-1\)
\(\dfrac{3x}{7}=\dfrac{-6}{7}\)
\(\Rightarrow3x=-6\)
\(x=\left(-6\right):3\)
\(x=-2\)
2. Thực hiện phép tính:
a) \(\dfrac{1}{2}+\dfrac{1}{2}.\dfrac{2}{3}-\dfrac{1}{3}:\dfrac{3}{4}+1\dfrac{4}{5}\)
\(=\dfrac{1}{2}.\left(\dfrac{2}{3}+1\right)-\dfrac{1}{3}:\dfrac{3}{4}+\dfrac{9}{5}\)
\(=\dfrac{1}{2}.\dfrac{5}{3}-\dfrac{1}{3}:\dfrac{3}{4}+\dfrac{9}{5}\)
\(=\dfrac{5}{6}-\dfrac{4}{9}+\dfrac{9}{5}\)
\(=\dfrac{7}{18}+\dfrac{9}{5}\)
\(=\dfrac{197}{90}\)
b) \(\dfrac{7.5^2-7^2}{7.24+21}\)
\(=\dfrac{7.25-7.7}{7.24+7.3}\)
\(=\dfrac{7.\left(25-7\right)}{7.\left(24+3\right)}\)
\(=\dfrac{7.18}{7.27}\)
\(=\dfrac{2}{3}\)
c) \(\dfrac{2}{3}+\dfrac{1}{3}.\left(\dfrac{-4}{9}+\dfrac{5}{6}\right):\dfrac{7}{12}\)
\(=\dfrac{2}{3}+\dfrac{1}{3}.\dfrac{7}{18}:\dfrac{7}{12}\)
\(=\dfrac{2}{3}+\dfrac{7}{54}:\dfrac{7}{12}\)
\(=\dfrac{2}{3}+\dfrac{2}{9}\)
\(=\dfrac{8}{9}\)
1,
x =( -12 . ( -3) ) : 2
x = 18
2,
a, -7/9 . 6/11 + (-2/9) = -14/33 + (-2/9) = -64/99
b, -4/7 : 2 = -4/7 . 1/2 = -2/7
c, 115 - (24 - 5. 3) = 115 - ( 24 - 15) = 115 - 9 = 106
d,= -3/7. (5/9 + 4/9) + 17/7 = -3/7 . 1 +17/7 = -3/7 . 17/7 = -51/49
e, ??? mình cx k biết
\(\dfrac{11}{5}-x=\dfrac{3}{5}:\dfrac{5}{3}\)
\(\dfrac{11}{5}-x=\dfrac{9}{25}\)
\(x=\dfrac{11}{5}-\dfrac{9}{25}=\dfrac{46}{25}\)
\(\dfrac{5}{3}\) \(\times\)[ 2\(\dfrac{1}{5}\) - \(x\)]\(^2\) = \(\dfrac{3}{5}\)
[\(\dfrac{11}{5}\) - \(x\)]2 = \(\dfrac{3}{5}\) : \(\dfrac{5}{3}\)
[ \(\dfrac{11}{5}\) - \(x\)]2 = \(\dfrac{3}{5}\) \(\times\) \(\dfrac{3}{5}\)
[ \(\dfrac{11}{5}\) - \(x\)]2 = \(\dfrac{9}{25}\)
\(\left[{}\begin{matrix}\dfrac{11}{5}-x=-\dfrac{3}{5}\\\dfrac{11}{5}-x=\dfrac{3}{5}\end{matrix}\right.\)
\(\left[{}\begin{matrix}x=\dfrac{11}{5}+\dfrac{3}{5}\\x=\dfrac{11}{5}-\dfrac{3}{5}\end{matrix}\right.\)
\(\left[{}\begin{matrix}x=\dfrac{14}{5}\\x=\dfrac{8}{5}\end{matrix}\right.\)
\(x\in\) { \(\dfrac{8}{5};\dfrac{14}{5}\)}
\(A=\dfrac{-19}{9}.\dfrac{1}{2}-\dfrac{4}{11}.\dfrac{-11}{9}+\left(-\dfrac{2}{3}\right)=-\dfrac{23}{18}\)
\(B=\left(-\dfrac{15}{6}\right):\dfrac{-1}{2}+\dfrac{7}{-12}-\dfrac{1}{3}.\dfrac{-11}{2}=\dfrac{25}{4}\)
\(C=\dfrac{3}{4}.\left(-8\right)-\dfrac{1}{3}.\dfrac{-7}{2}-\dfrac{5}{18}=-\dfrac{46}{9}\)
\(A=\dfrac{-19}{18}+\dfrac{4}{9}-\dfrac{2}{3}=\dfrac{-19}{18}+\dfrac{8}{18}-\dfrac{12}{18}=\dfrac{-23}{18}\)
\(B=\dfrac{-5}{2}\cdot\dfrac{-2}{1}-\dfrac{7}{12}+\dfrac{11}{6}=\dfrac{5\cdot12-7+22}{12}=\dfrac{75}{12}=\dfrac{25}{4}\)
Bài 1 :
a) \(x+2\dfrac{3}{4}=5\dfrac{2}{3}\)
\(x+\dfrac{11}{4}=\dfrac{17}{3}\)
\(x=\dfrac{17}{3}-\dfrac{11}{4}\)
\(x=\dfrac{35}{12}\)
Vậy .........................
b) \(x.3\dfrac{1}{2}=4\dfrac{3}{4}\)
\(x.\dfrac{7}{2}=\dfrac{19}{4}\)
\(x=\dfrac{19}{4}:\dfrac{7}{2}\)
\(x=\dfrac{19}{14}\)
Vậy .................
c) \(x:3\dfrac{1}{2}=4\dfrac{3}{4}\)
\(x:\dfrac{7}{2}=\dfrac{19}{4}\)
\(x=\dfrac{19}{4}.\dfrac{7}{2}\)
\(x=\dfrac{133}{8}\)
Vậy ...................
e) \(x-\dfrac{3}{4}=6.\dfrac{3}{8}\)
\(x-\dfrac{3}{4}=\dfrac{9}{4}\)
\(x=\dfrac{9}{4}+\dfrac{3}{4}\)
\(x=3\)
Vậy .............
f) \(\dfrac{7}{8}:x=3-\dfrac{1}{2}\)
\(\dfrac{7}{8}:x=\dfrac{5}{2}\)
\(x=\dfrac{7}{8}:\dfrac{5}{2}\)
\(x=\dfrac{7}{20}\)
Vậy ................
g) \(x+\dfrac{1}{2}.\dfrac{1}{3}=\dfrac{3}{4}\)
\(x+\dfrac{1}{6}=\dfrac{3}{4}\)
\(x=\dfrac{3}{4}-\dfrac{1}{6}\)
\(x=\dfrac{7}{12}\)
Vậy .................
h) \(x+17,67=100-63,2\)
\(x+17,67=36,8\)
\(x=36,8-17,67\)
\(x=19,13\)
Vậy ................
i) \(x:0,01=10\)
\(x=10.0,01\)
\(x=0,1\)
Vậy ...............
k) \(8,01-x=1,99\)
\(x=8,01-1,99\)
\(x=6,02\)
Vậy ............
l) \(x.0,5=2,2\)
\(x=2,2:0,5\)
\(x=4,4\)
Vậy ............
m) \(x:7,5=3,7+4,1\)
\(x:7,5=7,8\)
\(x=7,8.7,5\)
\(x=58,5\)
Vậy ............
\(x\times\dfrac{1}{2}+x\times\dfrac{3}{4}=\dfrac{7}{8}\\ x\times\left(\dfrac{1}{2}+\dfrac{3}{4}\right)=\dfrac{7}{8}\)
\(x\times\dfrac{10}{8}=\dfrac{7}{8}\\ x=\dfrac{7}{8}:\dfrac{10}{8}\\ x=\dfrac{7}{10}\)
a) \(\dfrac{2}{3}.x-\dfrac{1}{2}.x=\dfrac{5}{12}\)
=> \(\left(\dfrac{2}{3}-\dfrac{1}{2}\right).x=\dfrac{5}{12}\)
=> \(\left(\dfrac{4}{6}-\dfrac{3}{6}\right).x=\dfrac{5}{12}\)
=> \(\dfrac{1}{6}\) . x = \(\dfrac{5}{12}\)
=> \(x=\dfrac{5}{12}:\dfrac{1}{6}\)
=> x =\(\dfrac{5}{12}.\dfrac{6}{1}\)
=> x = \(\dfrac{5}{2}\)
Vậy x = \(\dfrac{5}{2}\)
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