Tìm x: a,7 |x|-24/3/14=|-3/11/14| b,3×(-2)^(5x+13) +24=0

Đáp án:

`a,`

$7 |x| – \dfrac{24}{\dfrac{3}{14} } =$ `|` $\dfrac{-3}{ \dfrac{11}{14} }$ `|`

`⇔ 7 |x| – 4/7 = | (-3)/154|`

`⇔7 |x| – 4/7 = 3/154`

`⇔ 7 |x| =  3/154 + 4/7`

`⇔ 7 |x| = 13/22`

`⇔ |x| = 13/22 ÷ 7`

`⇔ |x| = 13/154`

`⇔` \(\left[ \begin{array}{l}x=\dfrac{13}{154}\\x=\dfrac{-13}{154}\end{array} \right.\) 

Vậy `x=13/154` hoặc `x=(-13)/154`

$\\$

`b,`

`3 × (-2)^{5x + 13} + 24 = 0`

`⇔ 3 × (-2)^{5x + 13}=0-24`

`⇔ 3 × (-2)^{5x + 13} = -24`

`⇔ (-2)^{5x + 13} = -24 ÷ 3`

`⇔ (-2)^{5x + 13} = -8`

`⇔ (-2)^{5x + 13} = -2^3`

`⇔ 5x + 13 = 3`

`⇔ 5x = 3 – 13`

`⇔ 5x = -10`

`⇔x = -10 ÷ 5`

`⇔ x=-2`

Vậy `x=-2`