Đáp án:
C1:
a) \(\left\{ \begin{array}{l}
y = 50\\
x = 75\\
z = 30
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
C1:\\
a)\left\{ \begin{array}{l}
x = \dfrac{3}{2}y\\
z = \dfrac{3}{5}y\\
x + y - z = 95
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = \dfrac{3}{2}y\\
z = \dfrac{3}{5}y\\
\dfrac{3}{2}y + y - \dfrac{3}{5}y = 95
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = \dfrac{3}{2}y\\
z = \dfrac{3}{5}y\\
\dfrac{{19}}{{10}}y = 95
\end{array} \right. \to \left\{ \begin{array}{l}
y = 50\\
x = 75\\
z = 30
\end{array} \right.\\
b)\left\{ \begin{array}{l}
\dfrac{x}{9} - 3 = \dfrac{y}{5}\\
x = 30 - y
\end{array} \right.\\
\to \left\{ \begin{array}{l}
\dfrac{{30 - y - 27}}{9} = \dfrac{y}{5}\\
x = 30 - y
\end{array} \right.\\
\to \left\{ \begin{array}{l}
\dfrac{{3 - y}}{9} = \dfrac{y}{5}\\
x = 30 - y
\end{array} \right.\\
\to \left\{ \begin{array}{l}
15 - 5y = 9y\\
x = 30 - y
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = \dfrac{{15}}{{14}}\\
x = \dfrac{{405}}{{14}}
\end{array} \right.\\
C2:\\
Do:\dfrac{{a\dfrac{1}{b}}}{{b\dfrac{1}{a}}} = \dfrac{{\dfrac{{ab + 1}}{b}}}{{\dfrac{{ab + 1}}{a}}} = \dfrac{{ab + 1}}{b}:\dfrac{{ab + 1}}{a}\\
= \dfrac{{ab + 1}}{b}.\dfrac{a}{{ab + 1}} = \dfrac{a}{b}\\
\to dpcm
\end{array}\)
