Đáp án:
$d) x=23\\
e) x=3\\
f) x=4\\
g) x=4\\
h) {\left[\begin{aligned}x=6\\x=0\end{aligned}\right.}\\
i)
{\left[\begin{aligned}x=9\\x=-8\end{aligned}\right.}\\
j) x=5$
Giải thích các bước giải:
$d) 40-(3x-15):2=13\\
\Leftrightarrow (3x-15):2=40-13=27\\
\Leftrightarrow 3x-15=27.2=54\\
\Leftrightarrow 3x=54+15=69\\
\Leftrightarrow x=23\\
e) 2^{x+3}=64\\
\Leftrightarrow 2^{x+3}=2^6\\
\Leftrightarrow x+3=6\\
\Leftrightarrow x=6-3=3\\
f) 5^{x-1}=125\\
\Leftrightarrow 5^{x-1}=5^3\\
\Leftrightarrow x-1=3\\
\Leftrightarrow x=4\\
g) 5.3^{x-2}=45\\
\Leftrightarrow 3^{x-2}=9\\
\Leftrightarrow 3^{x-2}=3^2\\
\Leftrightarrow x-2=2\\
\Leftrightarrow x=4\\
h) (x-3)^2=9\\
\Leftrightarrow x-3=\pm 3\\
\Leftrightarrow {\left[\begin{aligned}x-3=3\\x-3=-3\end{aligned}\right.}\\
\Leftrightarrow {\left[\begin{aligned}x=6\\x=0\end{aligned}\right.}\\
i)
(x+4)^4=256\\
\Leftrightarrow x+4=\pm 4\\
\Leftrightarrow {\left[\begin{aligned}x+4=4\\x+4=-4\end{aligned}\right.}\\
\Leftrightarrow {\left[\begin{aligned}x=9\\x=-8\end{aligned}\right.}\\
j) (x-5)^4=(x-5)^5\\
\Leftrightarrow (x-5)^4-(x-5)^5=0\\
\Leftrightarrow (x-5)^4(1-x+4)=0\\
\Leftrightarrow (x-5)^4.(5-x)=0\\
\Leftrightarrow (5-x)^4.(5-x)=0\\
\Leftrightarrow (5-x)^5=0\\
\Leftrightarrow 5-x=0\\
\Leftrightarrow x=5$
