Given that f(x)=6x+5 find the value of f(a)+f(2a)

Question

I'm not sure how to solve this. I could really use your help!! I would really appreciate it if u explain if to me as simple as possible.Thanks !!

Answer 1

f(a) = 6a + 5

f(2a) = 6(2a) + 5 = 12a + 5

meaning that

f(a) + f(2a) = 6a + 5 + 12a + 5 = 18a + 10

Answer 2

f(x) = 6x+5

 

The notation f(a) is short for f(x=a).  Similarly, f(2a) is f(x=2a).  So just replace the x in the function with a or 2a:

f(x) = 6x + 5

 

f(a) = 6a + 5

 

f(2a) = 6(2a) + 5 = 12a + 5

 

So:

 

f(a) + f(2a) = 6a + 5 + 12a + 5

 

Combine like terms to get the answer.