Đáp án:
c) P=-5
Giải thích các bước giải:
\(\begin{array}{l}
a)Do:\left| x \right| = 3\\
\to \left[ \begin{array}{l}
x = 3\\
x = - 3
\end{array} \right.\\
Thay:\left[ \begin{array}{l}
x = 3\\
x = - 3
\end{array} \right.;y = 5\\
\to \left[ \begin{array}{l}
P = 2.3\left( {3 + 5} \right) - 3 + 5 - 5\\
P = 2.\left( { - 3} \right)\left( { - 3 + 5} \right) + 3 + 5 - 5
\end{array} \right.\\
\to \left[ \begin{array}{l}
P = 45\\
P = - 9
\end{array} \right.\\
b)\left\{ \begin{array}{l}
5x - 6y = - 1\\
x - y = 0
\end{array} \right.\\
\to \left\{ \begin{array}{l}
x = y\\
5y - 6y = - 1
\end{array} \right.\\
\to \left\{ \begin{array}{l}
y = 1\\
x = 1
\end{array} \right.\\
Thay:x = 1;y = 1\\
\to P = 2.1\left( {1 + 1} \right) - 1 + 5 - 1 = 6\\
c)Do:x + y = 0\\
P = 2x\left( {x + y} \right) - \left( {x + y} \right) - 5\\
= 2x.0 - 0 - 5 = - 5
\end{array}\)
