若 \(f\left( x \right) = 2x + 1\) ,則 \(f\left( 2 \right) = {\rm{?}}\)
(A) 3 (B) 4 (C) 5 (D) 6
詳解:函數對應之關係\(f(x) = 2x + 1\)
當 \(x = 2\) 時,對應到 \(f(2) = 2 \cdot 2 + 1 = 5\)
故選(C)