Bài 1:Tìm x biết:
a, (3,25- 2/3x).(-7/4)=-3
b,7/4-3/4:x=7/16
c,5/2-3/4x=4/5
d,3/5x+(-1)/2=-7/10
e,4/15:x+(-1)/3=5/9
Bài 1:Tìm x biết:
a, (3,25- 2/3x).(-7/4)=-3
b,7/4-3/4:x=7/16
c,5/2-3/4x=4/5
d,3/5x+(-1)/2=-7/10
e,4/15:x+(-1)/3=5/9
Đáp án:
e) \(x = \dfrac{3}{{10}}\)
Giải thích các bước giải:
\(\begin{array}{l}
a)\left( {\dfrac{{13}}{4} – \dfrac{2}{3}x} \right).\left( { – \dfrac{7}{4}} \right) = – 3\\
\to \dfrac{{13}}{4} – \dfrac{2}{3}x = \dfrac{{12}}{7}\\
\to \dfrac{2}{3}x = \dfrac{{43}}{{28}}\\
\to x = \dfrac{{129}}{{56}}\\
b)DK:x \ne 0\\
\dfrac{7}{4} – \dfrac{3}{4}:x = \dfrac{7}{{16}}\\
\to \dfrac{3}{4}:x = \dfrac{{21}}{{16}}\\
\to x = \dfrac{3}{4}:\dfrac{{21}}{{16}}\\
\to x = \dfrac{4}{7}\\
c)DK:x \ne 0\\
\dfrac{5}{2} – \dfrac{3}{{4x}} = \dfrac{4}{5}\\
\to \dfrac{3}{{4x}} = \dfrac{5}{2} – \dfrac{4}{5}\\
\to \dfrac{3}{{4x}} = \dfrac{{17}}{{10}}\\
\to x = \dfrac{{15}}{{34}}\\
d)\dfrac{3}{5}x – \dfrac{1}{2} = – \dfrac{7}{{10}}\\
\to \dfrac{3}{5}x = – \dfrac{1}{5}\\
\to x = – \dfrac{1}{3}\\
e)\dfrac{4}{{15}}:x – \dfrac{1}{3} = \dfrac{5}{9}\\
\to \dfrac{4}{{15}}:x = \dfrac{8}{9}\\
\to x = \dfrac{3}{{10}}
\end{array}\)
Đáp án + giải thích bước giải :
`a) (3,25 – 2/3x) . (-7/4) = -3`
`-> 3,25 – 2/3x = 12/7`
`-> 2/3x = 43/28`
`-> x= 129/56`
`b) 7/4 – 3/4 : x =7/16`
`-> 3/4 : x = 21/16`
`-> x = 4/7`
`c) 5/2 – 3/4x = 4/5`
`-> 3/4x = 17/10`
`-> x = 34/15`
`d) 3/5x + (-1/2) = -7/10`
`-> 3/5x = -1/5`
`-> x = -1/3`
`e) 4/15 : x + (-1/3) = 5/9`
`-> 4/15 : x= 8/9`
`-> x = 3/10`