SOLUTION: How do I solve this, please help me.. f(x)= 5x/4 + 2/3 What is f(a) if f(a+3)=5? Thanks!!

Algebra ->  Graphs -> SOLUTION: How do I solve this, please help me.. f(x)= 5x/4 + 2/3 What is f(a) if f(a+3)=5? Thanks!!      Log On


   



Question 1065260: How do I solve this, please help me..
f(x)= 5x/4 + 2/3
What is f(a) if f(a+3)=5?
Thanks!!

Answer by math_helper(2461) About Me  (Show Source):
You can put this solution on YOUR website!

f(a+3) = 5(a+3)/4 + 2/3
= (5/4)a + (15/4) + 2/3
= (5/4)a + (45/12) + (8/12)
= (5/4)a + (53/12)

We need to set the last line to 5 and then solve for 'a':
(5/4)a + (53/12) = 5
(5/4)a = (60/12) - (53/12)
(5/4)a = 7/12
a = (7/12)(4/5) = 28/60 = 7/15

Now that we've solved for 'a' (=7/15), you can plug this value in for 'x' in f(x) to find the function value at 'a'.
Can you finish it from here?