Question

Please help me Let f(x)=x^2+5 and g(x)= (x+5)/5 . find (g o f)(-3).

Answer 1

$f(x) = x^{2} + 5$                   $g(x) = \frac{x + 5}{5}$

First find gf(x) by substituting the expression for f(x) wherever there is an x in the g(x) function 

$gf(x) = \frac{( x^{2} + 5 ) + 5}{5}$

Simplify the equation and then substitute -3 where the x's are in gf(x)

gf(x) =  $\frac{ x^{2} + 10}{5}$

gf(-3)  =  $\frac{(-3)^{2} + 10 }{5}$
          
           =  $\frac{9 + 10}{5}$
 
           =  $\frac{19}{5}$

Keen to note that if you worked f(-3) first and then substituted that into g(x) then you would get the same answer.