Đáp án:
a. x = $\frac{17}{3}$
b. x = $\frac{-1}{11}$
e. \(\left[ \begin{array}{l}x=\frac{-5}{12}\\x=\frac{-13}{12}\end{array} \right.\)
g. \(\left[ \begin{array}{l}x=\frac{-7}{10}\\x=\frac{-4}{5}\end{array} \right.\)
i. $x = \frac{31}{8}$
l. x = $\frac{-2}{3}$
Giải thích các bước giải:
a. $3\frac{1}{2} - \frac{1}{2}x = \frac{2}{3}$
⇔ $\frac{7}{2} - \frac{x}{2} = \frac{2}{3}$
⇔ $\frac{x}{2} = \frac{7}{2} - \frac{2}{3}$
⇔ $\frac{x}{2} = \frac{17}{6}$
⇔ x = $\frac{17}{3}$
b. $\frac{1}{3} + \frac{2}{3} : x = - 7$ ( ĐKXĐ : x $\ne$ 0 )
⇔ $\frac{2}{3x} = -7 - \frac{1}{3}$
⇔ $\frac{2}{3x} = \frac{-22}{3}$
⇔ 3x×( -22 ) = 3×2
⇔ -66x = 6
⇔ x = $\frac{-1}{11}$ (TM)
e. $| x +\frac{3}{4} | - \frac{1}{3} = 0$
⇔$| x + \frac{3}{4} | = \frac{1}{3}$
⇔ \(\left[ \begin{array}{l}x+\frac{3}{4}=\frac{1}{3}\\x+\frac{3}{4}=\frac{-1}{3}\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=\frac{-5}{12}\\x=\frac{-13}{12}\end{array} \right.\)
g. $\frac{1}{5} + | x + \frac{3}{4} | = \frac{1}{4}$
⇔ $| x + \frac{3}{4} | = \frac{1}{20}$
⇔ \(\left[ \begin{array}{l}x+\frac{3}{4}=\frac{1}{20}\\x+\frac{3}{4}=\frac{-1}{20}\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=\frac{-7}{10}\\x=\frac{-4}{5}\end{array} \right.\)
i. $\frac{x-20}{5} = \frac{3}{8}$
⇔ 8×( x - 2 ) = 5×3
⇔ 8x = 15 + 16 = 31
⇔ $x = \frac{31}{8}$
l. $\frac{3}{2-3x} = \frac{6}{8}$ ( ĐKXĐ : x $\ne \frac{2}{3}$ )
⇔ 6×( 2 - 3x ) = 8×3
⇔ 18x = 12 - 24 = -12
⇔ x = $\frac{-12}{18}$
⇔ x = $\frac{-2}{3}$ (TM)
