Question

Tìm x, biết:

a ) x − 3 4 = 1 7   ;     b ) − x + 3 5 + 13 20 = 5 6

c ) x 2 − 2 5 = 1 10 ; d ) 15 x − 1 3 = 28 51

Answer 1

a ) x = 25 28 b ) x = 5 12 .

c) x= 1             d) x = 17

Answer 2

a; \(x\) - \(\dfrac{3}{4}\) = \(\dfrac{1}{7}\)

    \(x\)        = \(\dfrac{1}{7}\) + \(\dfrac{3}{4}\)

    \(x\)       =  \(\dfrac{4}{28}\) + \(\dfrac{21}{28}\)

    \(x\)       =  \(\dfrac{25}{28}\)

Vậy \(x=\dfrac{25}{28}\) 

Answer 3

b; - \(x\) + \(\dfrac{3}{5}\) + \(\dfrac{13}{20}\) = \(\dfrac{5}{6}\)

     (\(\dfrac{12}{20}\) + \(\dfrac{13}{20}\))  - \(x\) = \(\dfrac{5}{6}\)

    \(\dfrac{5}{4}\) - \(x\)  = \(\dfrac{5}{6}\) 

           \(x\) = \(\dfrac{5}{4}\) - \(\dfrac{5}{6}\)

           \(x\) = \(\dfrac{30}{24}\) -  \(\dfrac{20}{24}\)

            \(x\) = \(\dfrac{5}{12}\)

Vậy \(x=\dfrac{5}{4}\) 

Answer 4

c; \(\dfrac{x}{2}\) - \(\dfrac{2}{5}\) = \(\dfrac{1}{10}\)

    \(\dfrac{x}{2}\)        = \(\dfrac{1}{10}\) + \(\dfrac{2}{5}\)

     \(\dfrac{x}{2}\)       = \(\dfrac{1}{10}\) + \(\dfrac{4}{10}\)

       \(\dfrac{x}{2}\)     = \(\dfrac{1}{2}\)

        \(x\)      = \(\dfrac{1}{2}\) x 2

         \(x\)     = 1

    Vậy \(x\) = 1        

Answer 5

d; \(\dfrac{15}{x}\) - \(\dfrac{1}{3}\) = \(\dfrac{28}{51}\)

     \(\dfrac{15}{x}\) = \(\dfrac{28}{51}\) + \(\dfrac{1}{3}\)

      \(\dfrac{15}{x}\) = \(\dfrac{28}{51}\) + \(\dfrac{17}{51}\)

       \(\dfrac{15}{x}\) = \(\dfrac{45}{51}\)

         \(x\) = 15 : \(\dfrac{45}{51}\)

          \(x\) = 15 x \(\dfrac{51}{45}\)

           \(x\) = 17

Vậy \(x=17\)