High School

If [tex]f(x)=\left(\frac{1}{7}\right)\left(7^x\right)[/tex], what is [tex]f(3)[/tex]?



A. 343

B. [tex]\frac{1}{343}[/tex]

C. 49

D. [tex]\frac{1}{49}[/tex]

Answer :

- Substitute $x=3$ into the function $f(x) = \left(\frac{1}{7}\right)(7^x)$.
- Calculate $7^3 = 343$.
- Multiply $\frac{1}{7}$ by $343$ to get $\frac{343}{7}$.
- Simplify the fraction to find $f(3) = \boxed{49}$.

### Explanation
1. Understanding the problem
We are given the function $f(x) = \left(\frac{1}{7}\right)(7^x)$ and we need to find the value of $f(3)$. This means we need to substitute $x=3$ into the function and simplify.

2. Substitution
Substitute $x=3$ into the function: $f(3) = \left(\frac{1}{7}\right)(7^3)$.

3. Calculating 7 cubed
Calculate $7^3$: $7^3 = 7 \times 7 \times 7 = 49 \times 7 = 343$. So, $f(3) = \left(\frac{1}{7}\right)(343)$.

4. Simplifying the expression
Now, multiply $\frac{1}{7}$ by $343$: $f(3) = \frac{343}{7}$. To simplify this fraction, we can divide 343 by 7. The result is 49.

5. Final Answer
Therefore, $f(3) = 49$.

### Examples
Imagine you are tracking the growth of a plant where its height each day is given by the function $f(x) = \frac{1}{7} \cdot 7^x$, where $x$ is the number of days. Finding $f(3)$ tells you the height of the plant on the third day. This type of exponential function can model growth in various real-life scenarios, such as population growth or compound interest.