Bài 4:
a) /2x - 1/ = 5
⇒ $\left \{ {{2x - 1=5} \atop {2x-1=-5}} \right.$
⇒ $\left \{ {{2x =5+1} \atop {2x=-5+1}} \right.$
⇒ $\left \{ {{2x =6} \atop {2x=-4}} \right.$
⇒ $\left \{ {{x =6:2=3} \atop {x=-4:2=-2}} \right.$
b) /x - $\frac{4}{7}$/ = 1$\frac{3}{7}$
/x - $\frac{4}{7}$/ = $\frac{10}{7}$
⇒ $\left \{ {{x -\frac{4}{7}=\frac{10}{7}} \atop {x -\frac{4}{7}=\frac{-10}{7}}} \right.$
⇒ $\left \{ {{x =\frac{10}{7}+\frac{4}{7}=2} \atop {x =\frac{-10}{7}+\frac{4}{7}=\frac{-6}{7}}} \right.$
c) /x + $\frac{3}{4}$ / - $\frac{1}{3}$ = 0
/x + $\frac{3}{4}$ / = $\frac{1}{3}$
⇒$\left \{ {{x + \frac{3}{4}=\frac{1}{3}} \atop {x+ \frac{3}{4}=\frac{-1}{3}}} \right.$
⇒ $\left \{ {{x =\frac{1}{3}- \frac{3}{4}= \frac{-5}{12}} \atop {x=\frac{-1}{3}-\frac{3}{4}= \frac{-13}{12}}} \right.$
d) 0,2 - /4,2 - 2x/ = 0
/4,2 - 2x/ = 0,2
⇒ $\left \{ {{4,2 - 2x=0,2} \atop {4,2 - 2x=-0,2}} \right.$
⇒ $\left \{ {{2x=4,2-0,2=4} \atop {2x=4,2-(-0,2) = 4,4}} \right.$
⇒ $\left \{ {{x=4:2 = 2} \atop {x= 4,4:2=2,2}} \right.$
Bài 6:
a) x : $(\frac{3}{5}) ^{2}$ = $(\frac{3}{5}) ^{2}$
x = $(\frac{3}{5}) ^{2}$ . $(\frac{3}{5}) ^{2}$
x = $(\frac{3}{5}) ^{4}$
b) $2^{x-1}$ = 16
⇒ $2^{x-1}$ = $2^{4}$
⇒ x - 1 = 4
x = 4 + 1
x = 5
c) (x - 1)² = 25
⇒ (x - 1)² = 5²
⇒ x - 1 = 5
x = 5 + 1
x = 6
d) $(3x-1)^{4}$ = 81
⇒ $(3x-1)^{4}$ = $3^{4}$
⇒ 3x - 1 = 3
3x = 3 + 1
3x = 4
x = 4 : 3
x = $\frac{4}{3}$
