Question

a. 7x – 8 = 4 x + 7

b. \(\dfrac{2x-1}{3}\)- x+2=\(\dfrac{3x+5}{4}\)

Answer 1

a) \(7x-8=4x+7\)

\(\Leftrightarrow7x-4x=7+8\)

\(\Leftrightarrow3x=15\)

\(\Leftrightarrow x=5\)

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

\(\Leftrightarrow\dfrac{4\left(2x-1\right)-12x+24}{12}=\dfrac{3\left(3x+5\right)}{12}\)

\(\Leftrightarrow8x-4-12x+24=9x+15\)

\(\Leftrightarrow8x-12x-9x=15-24+4\)

\(\Leftrightarrow-13x=-5\)

\(\Leftrightarrow x=\dfrac{5}{13}\)

Answer 2

a) 7x-8=4x+7

<=> 7x-4x=7+8

<=>3x=15

<=> x=5

Vậy S={5}

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

\(\Leftrightarrow\dfrac{8x-4}{12}-\dfrac{12x}{12}+\dfrac{24}{12}=\dfrac{9x+15}{12}\)

\(\Rightarrow8x-4-12x+24=9x+15\)

\(\Leftrightarrow-13x=-5\Leftrightarrow x=\dfrac{5}{13}\)

Vậy S={\(\dfrac{5}{13}\)}