1. Tìm số nguyên x, y biết:
a) \(^{3^{4-x}}=27\)
b) \(^{3^{-1}}.^{4^x}+3.^{4^x}=\dfrac{5}{3}.^{2^7}\)
bài 2:tìm x, biết:
a. x + 1^3 = 2^5 - ( -1^3 )
b. 3^7 - x = 1^4 - ( -3^5 )
a) \(x+1^3=2^5-\left(-1^3\right)\)
\(\Rightarrow x+1=33\)
=> x = 32
b) \(3^7-x=1^4-\left(-3^5\right)\)
\(\Rightarrow2187-x=1+243=244\)
=> x = 1943
a) \(\Leftrightarrow x+1=32+1\)
\(\Leftrightarrow x=32\)
Vậy x = 32
b) \(\Leftrightarrow2187-x=1+243\)
\(\Leftrightarrow2187-x=244\)
\(\Leftrightarrow x=1943\)
Vậy x = 1943
a) \(x+1^3=2^5-\left(-1^3\right)\)
\(x+1=32-\left(-1\right)\)
\(x+1=33\)
\(x=33-1\)
\(x=32\)
b) \(3^7-x=1^4-\left(-3^5\right)\)
\(2187-x=1-\left(-243\right)\)
\(2187-x=244\)
\(x=2187-244\)
\(x=1943\)
Tìm x, biết:
a) \(\dfrac{4}{7}.x-\dfrac{2}{3}=\dfrac{1}{5};\)
b) \(\dfrac{4}{5}+\dfrac{5}{7}:x=\dfrac{1}{6}.\)
Lời giải:
a)
$\frac{4}{7}x=\frac{2}{3}+\frac{1}{5}=\frac{13}{15}$
$x=\frac{13}{15}:\frac{4}{7}=\frac{91}{60}$
b)
$\frac{5}{7}:x=\frac{1}{6}-\frac{4}{5}$
$\frac{5}{7}:x=\frac{-19}{30}$
$x=\frac{5}{7}:\frac{-19}{30}=\frac{-150}{133}$
a) \(\dfrac{4}{7}.x-\dfrac{2}{3}=\dfrac{1}{5}\)
\(\dfrac{4}{7}.x=\dfrac{1}{5}+\dfrac{2}{3}\)
\(\dfrac{4}{7}.x=\dfrac{13}{15}\)
\(x=\dfrac{13}{15}:\dfrac{4}{7}\)
\(x=\dfrac{91}{60}\)
b) \(\dfrac{4}{5}+\dfrac{5}{7}:x=\dfrac{1}{6}\)
\(\dfrac{5}{7}:x=\dfrac{1}{6}-\dfrac{4}{5}\)
\(\dfrac{5}{7}:x=\dfrac{-19}{30}\)
\(x=\dfrac{5}{7}:\dfrac{-19}{30}\)
\(x=\dfrac{-150}{133}\)
Tìm x biết:
a) \(x:1\frac{2}{7} = - 3,5\)
b) \(0,4.x - \frac{1}{5}.x = \frac{3}{4}\)
a) \(1\frac{2}{7} = 1 + \frac{2}{7} = \frac{9}{2}\)
\(\begin{array}{l}x:1\frac{2}{7} = - 3,5\\x:\frac{9}{7} = - \frac{7}{2}\\x = - \frac{7}{2}.\frac{9}{7}\\x = - \frac{9}{2}\end{array}\)
b) \(0,4.x - \frac{1}{5}.x = \frac{3}{4}\)
\(\begin{array}{l}\frac{2}{5}.x - \frac{1}{5}.x = \frac{3}{4}\\\left( {\frac{2}{5} - \frac{1}{5}} \right).x = \frac{3}{4}\\\frac{1}{5}.x = \frac{3}{4}\\x = \frac{3}{4}:\frac{1}{5}\\x = \frac{3}{4}.5\\x = \frac{{15}}{4}\end{array}\)
Tìm x, biết:
a)\(x + \frac{1}{2} = - \frac{1}{3};\) b)\(\left( { - \frac{2}{7}} \right) + x = - \frac{1}{4}\)
a)
\(\begin{array}{l}x + \frac{1}{2} = - \frac{1}{3}\\x = - \frac{1}{3} - \frac{1}{2}\\x = - \frac{2}{6} - \frac{3}{6}\\x = \frac{{ - 5}}{6}\end{array}\)
Vậy \(x = \frac{{ - 5}}{6}\).
b)
\(\begin{array}{l}\left( { - \frac{2}{7}} \right) + x = - \frac{1}{4}\\x = - \frac{1}{4} - \left( { - \frac{2}{7}} \right)\\x = - \frac{1}{4} + \frac{2}{7}\\x = - \frac{7}{{28}} + \frac{8}{{28}}\\x = \frac{1}{{28}}\end{array}\)
Vậy \(x = \frac{1}{{28}}\).
tìm x , biết:
a) \(x\) : \(4\dfrac{1}{3}\) = -2,5 b) \(\dfrac{3}{5}x\) + \(\dfrac{1}{4}\) = \(\dfrac{1}{10}\)
c) \(2\dfrac{7}{9}\) \(-\) \(\dfrac{12}{13}x\) = \(\dfrac{7}{9}\) d)\(\dfrac{-2}{3}-\dfrac{1}{3}\)\(\left(2x-5\right)=\dfrac{3}{2}\)
a, \(x\) : \(\dfrac{13}{3}\) = -2,5
\(x\) = -2,5 . \(\dfrac{13}{3}\)
\(x\) = \(\dfrac{65}{6}\)
b,\(\dfrac{3}{5}\)\(x\) = \(\dfrac{1}{10}-\)\(\dfrac{1}{4}\)
\(\dfrac{3}{5}x\) = \(\dfrac{-3}{20}\)
\(x\) = \(\dfrac{-3}{20}\) : \(\dfrac{3}{5}\)
\(x\) = \(\dfrac{-1}{4}\)
c, \(\dfrac{25}{9}-\dfrac{12}{13}x=\dfrac{7}{9}\)
\(\dfrac{12}{13}x\)\(=\dfrac{25}{9}-\dfrac{7}{9}\)
\(\dfrac{12}{13}x=2\)
\(x=2:\dfrac{12}{13}\)
\(x=\dfrac{13}{6}\)
Tìm x, biết:
a) \(x-\dfrac{5}{6}=\dfrac{1}{2};\)
b) \(\dfrac{-3}{4}-x=\dfrac{-7}{12}.\)
\(a.\)
\(x-\dfrac{5}{6}=\dfrac{1}{2}\)
\(\Leftrightarrow x=\dfrac{1}{2}+\dfrac{5}{6}=\dfrac{3+5}{6}=\dfrac{8}{6}=\dfrac{4}{3}\)
\(b.\)
\(-\dfrac{3}{4}-x=-\dfrac{7}{12}\)
\(\Leftrightarrow x=-\dfrac{3}{4}--\dfrac{7}{12}=-\dfrac{3}{4}+\dfrac{7}{12}=\dfrac{\left(-3\right)\cdot3+7}{12}=\dfrac{-2}{12}=-\dfrac{1}{6}\)
a)x=1/2+5/6
x=/3/6+5/6
x=8/6=4/3
b)x=-3/4- (-7/12)
x=-9/12-(-7/12)
x=-1/6
a) \(x-\dfrac{5}{6}=\dfrac{1}{2}\)
\(x=\dfrac{1}{2}+\dfrac{5}{6}\)
\(x=\dfrac{4}{3}\)
b) \(\dfrac{-3}{4}-x=\dfrac{-7}{12}\)
\(x=\dfrac{-3}{4}-\dfrac{-7}{12}\)
\(x=\dfrac{-1}{6}\)
Tìm x biết:
a) (x - 4)^2 = (x - 4)
b) 5x^2(x - 7) - 7(7 - x) = 0
c) x^3 - 3x^2 - x + 3 = 0
d) x^3 - 4x + x - 4 = 0
a) \(\left(x-4\right)^2-\left(x-4\right)=0\)
\(\left(x-4\right)\left(x-4-1\right)=0\)
\(\left[{}\begin{matrix}x-4=0\\x-5=0\end{matrix}\right.\)
\(\left[{}\begin{matrix}x=4\\x=5\end{matrix}\right.\)
b) \(5x^2\left(x-7\right)+7\left(x-7\right)=0\)
\(\left(x-7\right)\left(5x^2+7\right)=0\)
\(\left[{}\begin{matrix}x-7=0\\5x^2+7=0\end{matrix}\right.\)
\(\left[{}\begin{matrix}x=7\\x^2=\dfrac{-7}{5}\end{matrix}\right.\)
\(x=7\)
c) \(x^2\left(x-3\right)-\left(x-3\right)=0\)
\(\left(x-3\right)\left(x^2-1\right)=0\)
\(\left[{}\begin{matrix}x=3\\x=\pm1\end{matrix}\right.\)
a) (x - 4)^2=(x - 4)
(x - 4) (x -4)=(x -4 )
(x - 4) (x - 4)-(x - 4)=0
(x-4) (x-4-1)=0
(x-4) (x-5)=0
TH1:x-4=0 TH2:x-5=0
x=4 x=5
Tìm x,biết:
a,(1/2 + 4/7) : x =_ 3/4
b, 0,5 . x - 1 3/4 = 25 phần trắm
a, \(\left(\dfrac{1}{2}+\dfrac{4}{7}\right):x=\dfrac{-3}{4}\)
\(\dfrac{15}{14}:x=\dfrac{-3}{4}\)
=> x= \(\dfrac{-7}{10}\)
b, 0,5:x-\(1\dfrac{3}{4}\)= 25%
0,5:x-\(\dfrac{7}{4}=\dfrac{1}{4}\)
0,5:x = 2
=> x = \(\dfrac{1}{4}\)
Tìm x, biết:
a) \(\left(3\dfrac{1}{2}-2.x\right).3\dfrac{1}{3}=7\dfrac{1}{3}\)
b) \(\dfrac{4}{9}.x=\dfrac{9}{8}-0,125\)
c) \(\dfrac{-X}{21}=\dfrac{20}{7}\)
a, \(\left(\dfrac{7}{2}-2x\right).\dfrac{10}{3}=\dfrac{22}{3}\Leftrightarrow\dfrac{7}{2}-2x=\dfrac{22}{10}=\dfrac{11}{5}\)
\(\Leftrightarrow2x=\dfrac{13}{10}\Leftrightarrow x=\dfrac{13}{20}\)
b, \(\dfrac{4x}{9}=\dfrac{9}{8}-\dfrac{125}{1000}=1\Leftrightarrow x=\dfrac{9}{4}\)
c, \(-\dfrac{x}{21}=\dfrac{60}{21}\Rightarrow x=-60\)
