Đáp án: + Giải thích các bước giải:
a) $\dfrac{1}{5} +\dfrac{4}{5}. (x-2 ) = -3$
$\dfrac{4}{5}. (x-2 ) = \dfrac{-16}{5}$
$x- 2 = -4$
$x = -2$
b)
$4(x-\dfrac{1}{2})² = 9$
$(x-\dfrac{1}{2})² = \dfrac{9}{4}$
$(x-\dfrac{1}{2})² = (\dfrac{3}{2})²$
$x-\dfrac{1}{2} = ±\dfrac{3}{2}$
\(\left[ \begin{array}{l}x=2\\x=-1\end{array} \right.\)
c)
$\dfrac{1}{3}x + \dfrac{2}{5}x - \dfrac{1}{4} = \dfrac{2}{3}$
$\dfrac{11}{15}x = \dfrac{11}{12}$
$x = \dfrac{5}{4}$
