Question

f(x+1)= 3x+5 then evaluate f(-2) and f(2x) with process
​

Answer 1

$\large\underline\purple{\bold{Solution :- }}$

$\tt \longrightarrow \: f(x + 1) = 3x + 5$

☆ Put x + 1 = y, we get x = y - 1, so above expression can be rewritten as

$\tt \longrightarrow \: f(y) = 3(y - 1) + 5 \\ \tt \longrightarrow \: f(y) = 3y - 3 + 5 \: \: \: \\ \tt\implies \:f(y) \: = \: 3y \: + \: 2 \: \: \: \: \: \:$

$\tt \longrightarrow \: So, \: f( - 2) = 3( - 2) + 2 = - 6 + 2 = - 4$

$\tt \longrightarrow \: and \: f(2x) = 3(2x) + 2 = 6x + 2$