Đáp án:
$5)
a)500\\
b)
1\\
c)\dfrac{9}{20}\\
6)
a)x=2005\\
b) {\left[\begin{aligned}x=16\\x=-6\end{aligned}\right.}\\
c) x=4$
Giải thích các bước giải:
$5)
a)36+(-83)+564-17=(36+564)+(-83-17)=600+(-100)=500\\
b)
\dfrac{-5}{7}.\dfrac{2}{11}+\dfrac{-5}{7}.\dfrac{9}{11}+1\dfrac{5}{7}\\
=\dfrac{-5}{7}.\dfrac{2}{11}+\dfrac{-5}{7}.\dfrac{9}{11}+\dfrac{12}{7}\\
=\dfrac{-5}{7}.\left ( \dfrac{2}{11}+\dfrac{9}{11}\right )+\dfrac{12}{7}\\
=\dfrac{-5}{7}+\dfrac{12}{7}\\
=1\\
c)\dfrac{75}{100}-1\dfrac{1}{2}+0,5:\dfrac{5}{12}\\
=\dfrac{3}{4}-\dfrac{3}{2}+\dfrac{1}{2}.\dfrac{12}{5}\\
=\dfrac{3}{4}-\dfrac{3}{2}+\dfrac{6}{5}\\
=\dfrac{15}{20}-\dfrac{30}{20}+\dfrac{24}{50}\\
=\dfrac{9}{20}\\
6)
a)x+5=2015-(12-7)\\
\Leftrightarrow x=2015-5-5=2005\\
b)\left | x-5 \right |=11\\
\Leftrightarrow {\left[\begin{aligned}x-5=11\\x-5=-11\end{aligned}\right.}\\
\Leftrightarrow {\left[\begin{aligned}x=16\\x=-6\end{aligned}\right.}\\
c)2^{x-1}=8\\
\Leftrightarrow 2^{x-1}=2^3\\
\Leftrightarrow x-1=3\\
\Leftrightarrow x=4$
