SOLUTION: Hi, Can you help me with this math problem? 13.) Find the function value. Let f(x) =5x.Find f(-2) The answer should be 1 over 25

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: Hi, Can you help me with this math problem? 13.) Find the function value. Let f(x) =5x.Find f(-2) The answer should be 1 over 25       Log On


   

Question 135651: Hi,
Can you help me with this math problem?
13.) Find the function value.
Let f(x) =5x.Find f(-2)
The answer should be 1 over 25
Found 2 solutions by stanbon, solver91311:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Let f(x) =5^x.
Find f(-2)
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f(-2) = 5^(-2)
The negative means "inverse".
The 2 means "square".
You may carry these two operations in any order.
--------------------
f(-2) = (1/5)2 = 1/25
OR
f(-2) = 25^-1 = 1/25
======================
Cheers,
Stan H.

Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!
Only if the function is acutually f%28x%29=5%5Ex.

If the function is f%28x%29=5x, then f%28-2%29=5%28-2%29=-10,

But if f%28x%29=5%5Ex, then f%28-2%29=5%5E%28-2%29

Remember the rules for exponents: a%5E%28-n%29=1%2Fa%5En, so:

f%28-2%29=5%5E%28-2%29=1%2F5%5E2=1%2F25

Hint: When indicating something should be raised to a power, use the caret mark "^" (shift-6). x^2 is x squared, 5^x is 5 to the x power.