The number of functions \(f:\left\{1,2,3,4\right\}\to \left\{a,b,c\right\}\) which are not onto, is: [JEE Main 2026, 4 A…

Number of functions which are not onto
\(=(\)Total number of functions possible\()-(\)Number of onto functions \() \)
\( =3^4-\left(3^4-{ }^3 C_1(3-1)^4+{ }^3 C_2(3-2)^4\right) \)
\(= 3(2)^4-3(1) \)
\(=48-3=45\)