در شکل رو به رو، c کدام است؟
\(c = 2a - b\)
\(c = a - 2b\)
\(c = 2a + b\)
\(c = a + b\)
\(\left. \begin{array}{l}c = x + b\\\\x = a + a = 2a\end{array} \right\} \Rightarrow c = 2a + b\)