SOLUTION: Need help with a problem. If f(x)=(x-3A)/3x+4 and f(3)=6, what is the value of A?

Algebra ->  Matrices-and-determiminant -> SOLUTION: Need help with a problem. If f(x)=(x-3A)/3x+4 and f(3)=6, what is the value of A?      Log On


   

Question 966106: Need help with a problem. If f(x)=(x-3A)/3x+4 and f(3)=6, what is the value of A?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Plug in x = 3 and use this to find A


f%28x%29=%28x-3A%29%2F%283x%2B4%29


f%283%29=%283-3A%29%2F%283%2A3%2B4%29 Replace every x with 3. Since x = 3 when we say f(3)


f%283%29=%283-3A%29%2F%2813%29


6=%283-3A%29%2F%2813%29 Replace f(3) with 6. Since f(3) = 6. Now we isolate A


6%2A13=3-3A


78=3-3A


78%2B3A=3


3A=3-78


3A=-75


A=-75%2F3


A=-25

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