Respuesta :
f(x) = 3x +1 so than f(a+1) will get easy just substituted the (a+1) in place of x inside equation in this way
f(a+1) = 3(a+1) +1
f(a+1) = 3a +3 +1
f(a+1) = 3a +4
hope this will help you
f(a+1) = 3(a+1) +1
f(a+1) = 3a +3 +1
f(a+1) = 3a +4
hope this will help you