Question

Let f(x) = x2 + 6 and g(x) = x + 8x . Find ( g o f)(­ -7)

Answer 1

Answer:
`(gof)(-7) =495`

Explanation:

Given the functions f(x) and g(x), to find
`(gof)(x)` you need to substitute
`x=f(x)=x^2 + 6` into the function g(x):

`(gof)(x) = ( x^2 + 6)+ 8( x^2 + 6)\\\\(gof)(x)=x^2 + 6+ 8x^2 + 48\\\\(gof)(x)=9x^2 + 54`

Now, to find
`(gof)(-7)` you must substitute
`x=-7` into
`(gof)(x)`, then you get:

`(gof)(-7) = 9(-7)^2 + 54\\\\(gof)(-7) =9(49)+54\\\\(gof)(-7) =441+54\\\\(gof)(-7) =495`