a) ( 15 + x ) : 3 = 3^15 : 312 b) 525 . 5^x – 1 = 5^25 c) ( 2x – 4 ) ^2 = 64 04/07/2021 Bởi Eloise a) ( 15 + x ) : 3 = 3^15 : 312 b) 525 . 5^x – 1 = 5^25 c) ( 2x – 4 ) ^2 = 64
Đáp án: `a) (15+x):3=3^15:3^12` `⇔(15+x):3=3^3` `⇔15+x=3^4` `⇔15+x=81` `⇔x=81-15` `⇔x=66` `b) 5^25.(5^x-1)=5^25` `⇔5^x-1=1` `⇔5^x=2` `⇒` pt vô nghiệm okay :3 `c) (2x-4)^2=64` TH1: `(2x-4)^2=8^2` `⇔2x-4=8` `⇔2x=12` `⇔x=6` TH2: `(2x-4)^2=(-8)^2` `⇔2x-4=-8` `⇔2x=-4` `⇔x=-2` Bình luận
Giải thích các bước giải: $(15+x):3=3^{15}:3^{12}$ $⇔15+x=3.3^{15}:3^{12}$ $⇔15+x=3^{16}:3^{12}$ $⇔15+x=3^4$ $⇔x=3^4-15$ $⇔x=81-15$ $⇔x=66$ $\text{Vậy $x=66$}$ $\text{b) Xem lại đề}$ $c)(2x-4)^2=64$ $⇔(2x-4)^2=±8$ $⇔$ \(\left[ \begin{array}{l}2x-4=8\\2x-4=-8\end{array} \right.\) $⇔$ \(\left[ \begin{array}{l}2x=12\\2x=-4\end{array} \right.\) $⇔$ \(\left[ \begin{array}{l}x=6\\x=-2\end{array} \right.\) $\text{Vậy $x∈\{-2;6\}$}$ Học tốt!!! Bình luận
Đáp án:
`a) (15+x):3=3^15:3^12`
`⇔(15+x):3=3^3`
`⇔15+x=3^4`
`⇔15+x=81`
`⇔x=81-15`
`⇔x=66`
`b) 5^25.(5^x-1)=5^25`
`⇔5^x-1=1`
`⇔5^x=2`
`⇒` pt vô nghiệm okay :3
`c) (2x-4)^2=64`
TH1: `(2x-4)^2=8^2`
`⇔2x-4=8`
`⇔2x=12`
`⇔x=6`
TH2: `(2x-4)^2=(-8)^2`
`⇔2x-4=-8`
`⇔2x=-4`
`⇔x=-2`
Giải thích các bước giải:
$(15+x):3=3^{15}:3^{12}$
$⇔15+x=3.3^{15}:3^{12}$
$⇔15+x=3^{16}:3^{12}$
$⇔15+x=3^4$
$⇔x=3^4-15$
$⇔x=81-15$
$⇔x=66$
$\text{Vậy $x=66$}$
$\text{b) Xem lại đề}$
$c)(2x-4)^2=64$
$⇔(2x-4)^2=±8$
$⇔$ \(\left[ \begin{array}{l}2x-4=8\\2x-4=-8\end{array} \right.\) $⇔$ \(\left[ \begin{array}{l}2x=12\\2x=-4\end{array} \right.\) $⇔$ \(\left[ \begin{array}{l}x=6\\x=-2\end{array} \right.\)
$\text{Vậy $x∈\{-2;6\}$}$
Học tốt!!!