Tìm x a, ( x + 3/4 ) ² = 4/25 b, ( 4/7 – 1/2 x ) ³ = 8 C, x³ = -8 D, 9^x-1 = 1/9

$a, ( x + \dfrac{3}{4} ) ² = \dfrac{4}{25}$

$ ( x+ \dfrac{3}{4})²$ = $\frac{2²}{5²}$

$ x + \dfrac{3}{4}$ = $±\dfrac{2}{5}$

TH1:

$ x + \dfrac{3}{4}$ = $\dfrac{2}{5}$ 

$x = \dfrac{2}{5}$ – $\dfrac{3}{4}$

$x =\dfrac{-7}{20} $

TH2:

$ x + \dfrac{3}{4} = -\dfrac{2}{5}$ 

$x =-\dfrac{2}{5} -\dfrac{3}{4}$

$x =\dfrac{-23}{20} $

$b, ( \dfrac{4}{7} – \dfrac{1}{2}x ) ³ = 8$

$( \dfrac{4}{7} -\dfrac{1}{2}x ) ³ = 2³$

$\dfrac{4}{7} -\dfrac{1}{2}x = 2$

$ -\dfrac{1}{2}x $=  2- $\dfrac{4}{7} $

$ -\dfrac{1}{2}x$ = $\dfrac{10}{7} $

$x = \dfrac{10}{7} $ : $\dfrac{-1}{2} $

$x = \dfrac{20}{7}$

$c, x³ = -8$

$x³ = -2³$

$x = -2$

$D, 9^{x-1} =\dfrac{1}{9} $

$9^{x-1} =9^{-1}$

$x – 1 = -1 $

$x = -1 +1 $

$x = 0 $

#no copy #