Question

Tìm  x, biết rằng:

a)  5 8 x + 2 5 = 1 5

b)  5 7 : x + 11 7 = 18 7

c)  2 x 5 − 1 : − 5 = 1 7

Answer 1

a) 

5 8 x + 2 5 = 1 5 5 8 x             = 1 5 − 2 5 5 8 x            = − 1 5 x               = − 1 5 : 5 8 x                = − 1 5 . 8 5 x               = − 8 25

b)

5 7 : x + 11 7 = 18 7 5 7 : x            = 18 7 − 11 7 5 7 : x             = 1 x                 = 5 7 : 1 x                = 5 7

c)

2 x 5 − 1 : − 5 = 1 7 2 x 5 − 1         = 1 7 . − 5 2 x 5 − 1       = − 5 7 2 x 5              = − 5 7 + 1 2 x 5              = 2 5 x                 = 2 5 : 2 5 x                 = 1

Answer 2

a,\(\frac{5}{8}x+\frac{2}{5}=\frac{1}{5}\)

\(< =>\frac{5}{8}x=\frac{1}{5}-\frac{2}{5}\)

\(< =>\frac{5}{8}x=-\frac{1}{5}\)

\(< =>x=-\frac{1}{5}:\frac{5}{8}=-\frac{8}{25}\)

Answer 3

\(\frac{5}{7}:x+\frac{11}{7}=\frac{18}{7}\)

\(< =>\frac{5}{7}.\frac{1}{x}=\frac{18}{7}-\frac{11}{7}\)

\(< =>\frac{5}{7x}=\frac{7}{7}=1\)

\(< =>7x=5< =>x=\frac{5}{7}\)

Answer 4

\(\left(\frac{2x}{5}-1\right):\left(-5\right)=\frac{1}{7}\)

\(< =>\frac{2x}{5}-1=\frac{1}{7}.\left(-5\right)\)

\(< =>\frac{2x}{5}-1=-\frac{5}{7}\)

\(< =>\frac{2x}{5}=-\frac{5}{7}+1=\frac{2}{7}\)

\(< =>2x.7=5.2\)

\(< =>x=\frac{10}{14}=\frac{5}{7}\)