Tìm x biết: a) 2/5 - |1/2 -x| = 6 b) |3/8 - x| + 5/6 = 7/4

* Hướng dẫn giải

a) $\frac{2}{5}-\left|\frac{1}{2}-x\right|=6\iff \left|\frac{1}{2}-x\right|=-\frac{28}{5}$

Mà $\left|\frac{1}{2}-x\right|\ge 0_{}\forall x$$\Rightarrow x\in \varnothing$

b) $\left|\frac{3}{8}-x\right|+\frac{5}{6}=\frac{7}{4}\iff \left|\frac{3}{8}-x\right|=\frac{11}{12}$

$\iff \left[\begin{array}{l}\frac{3}{8}-x=-\frac{11}{12}\\ \frac{3}{8}-x=\frac{11}{12}\end{array}\right.\iff \left[\begin{array}{l}x=\frac{31}{24}\\ x=-\frac{13}{24}\end{array}\right.$