tìm x
a ) 2/7 + x = -5/4
b ) x – 11/7 = 13/3
c ) 12/5 – x = -9/4
d ) -x – 4/5 = -6/5
e ) 2/3 – ( -1/2 – x ) = -4/5
f ) 3/7 – x = 1/4 – ( -3 / 5 )
g ) -21/10 . x + 1/3 = -2/3
h) 8/15 : x = -20 / 21
i ) x : ( -4/21) = 14/5
giúp vs ạ
tìm x a ) 2/7 + x = -5/4 b ) x – 11/7 = 13/3 c ) 12/5 – x = -9/4 d ) -x – 4/5 = -6/5 e ) 2/3 – ( -1/2 – x ) = -4/5 f ) 3/7 – x = 1/4 – ( -3 / 5
By Eloise
Đáp án:
$\begin{array}{l}
a)\dfrac{2}{7} + x = \dfrac{{ – 5}}{4}\\
x = \dfrac{{ – 5}}{4} – \dfrac{2}{7}\\
x = \dfrac{{ – 35 – 8}}{{28}}\\
x = – \dfrac{{43}}{{28}}\\
Vậy\,x = \dfrac{{ – 43}}{{28}}\\
b)x – \dfrac{{11}}{7} = \dfrac{{13}}{3}\\
x = \dfrac{{13}}{3} + \dfrac{{11}}{7}\\
x = \dfrac{{91 + 33}}{{21}}\\
x = \dfrac{{124}}{{21}}\\
Vậy\,x = \dfrac{{124}}{{21}}\\
c)\dfrac{{12}}{5} – x = \dfrac{{ – 9}}{4}\\
x = \dfrac{{12}}{5} – \left( { – \dfrac{9}{4}} \right)\\
x = \dfrac{{12}}{5} + \dfrac{9}{4}\\
x = \dfrac{{93}}{{20}}\\
Vậy\,x = \dfrac{{93}}{{20}}\\
d) – x – \dfrac{4}{5} = \dfrac{{ – 6}}{5}\\
x = \dfrac{{ – 4}}{5} + \dfrac{6}{5}\\
x = \dfrac{2}{5}\\
e)\dfrac{2}{3} – \left( { – \dfrac{1}{2} – x} \right) = \dfrac{{ – 4}}{5}\\
\dfrac{2}{3} + \dfrac{1}{2} + x = \dfrac{{ – 4}}{5}\\
x = – \dfrac{4}{5} – \dfrac{2}{3} – \dfrac{1}{2}\\
x = \dfrac{{ – 24 – 20 – 15}}{{30}}\\
x = \dfrac{{ – 59}}{{30}}\\
Vậy\,x = \dfrac{{ – 59}}{{30}}\\
g)\dfrac{{ – 21}}{{10}}.x + \dfrac{1}{3} = \dfrac{{ – 2}}{3}\\
\dfrac{{ – 21}}{{10}}.x = \dfrac{{ – 2}}{3} – \dfrac{1}{3} = – 1\\
x = \dfrac{{10}}{{21}}\\
Vậy\,x = \dfrac{{10}}{{21}}\\
h)\dfrac{8}{{15}}:x = \dfrac{{ – 20}}{{21}}\\
x = \dfrac{8}{{15}}:\dfrac{{ – 20}}{{21}}\\
x = \dfrac{8}{{15}}.\dfrac{{ – 21}}{{20}}\\
x = \dfrac{{ – 14}}{{25}}\\
Vậy\,x = \dfrac{{ – 14}}{{25}}\\
i)x:\left( { – \dfrac{4}{{21}}} \right) = \dfrac{{14}}{5}\\
x = \dfrac{{14}}{5}.\dfrac{{ – 4}}{{21}}\\
x = \dfrac{{ – 8}}{{15}}\\
Vậy\,x = \dfrac{{ – 8}}{{15}}
\end{array}$