Question

Tìm x

a) \(\dfrac{1}{2}\)x + \(\dfrac{1}{8}\)x = \(\dfrac{3}{4}\)

b) ( 2x -4,5 ) : \(\dfrac{3}{4}\) - \(\dfrac{1}{3}\) = 1

Answer 1

a)

\(\dfrac{1}{2}x+\dfrac{1}{8}x=\dfrac{3}{4}\\ x\left(\dfrac{1}{2}+\dfrac{1}{8}\right)=\dfrac{3}{4}\\ x\cdot\dfrac{5}{8}=\dfrac{3}{4}\\ x=\dfrac{3}{4}:\dfrac{5}{8}=\dfrac{6}{5}\)

b)

\(\left(2x-4,5\right):\dfrac{3}{4}-\dfrac{1}{3}=1\\\left(2x-\dfrac{9}{2}\right):\dfrac{3}{4}-\dfrac{1}{3}=1\\ \left(2x-\dfrac{9}{2}\right):\dfrac{3}{4}=1+\dfrac{1}{3}=\dfrac{4}{3}\\ \left(2x-\dfrac{9}{2}\right)=\dfrac{4}{3}\cdot\dfrac{3}{4}=1\\ 2x=1+\dfrac{9}{2}=\dfrac{11}{2}\\ x=\dfrac{11}{2}:2=\dfrac{11}{4}\)

Answer 2

a) 1/2 . x + 1/8 . x = 3/4

<=> ( 1/2 + 1/8 ) . x = 3/4

<=> ( 4/8 + 1/8 ) . x = 3/4

<=> 5/8 . x = 3/4

<=> x = 3/4 . 8/5

<=> x = 6/5

Vậy x = 6/5

b) ( 2x - 4,5 ) : 3/4 - 1/3 = 1

<=> ( 2x - 45/10 ) : 3/4 - 1/3 = 1

<=> ( 2x - 9/2 ) : 3/4 - 1/3 = 1

<=> ( 2x - 9/2 ) : 3/4 = 1 + 1/3

<=> ( 2x - 9/2 ) : 3/4 = 4/3

<=> 2x - 9/2 = 4/3 . 3/4

<=> 2x - 9/2 = 1

<=> 2x = 1 + 9/2

<=> 2x = 11/2

<=> x = 11/2 . 1/2

<=> x = 11/4

Vậy x = 11/4