
In a equation in the exponential general form you have:
a is the y-intercetp: the value of the function when x is 0)
For the given function the y intercept is (0,5), then
a=5

Use the given point (2,45) to find the value of b
y=45
x=2

Divide both sides of the equation into 5:

Find the square root in both sides of the equation:
![\begin{gathered} \sqrt[]{9}=\sqrt[]{b^2} \\ \\ 3=b \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/zpand5l1oc0unnz544khhp20gv114n9i77.png)
Then, for the given function you have the next equation:

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To find the value of the function when x=4 use the equation above, substitute the x for 4 and evaluate:

Then, when x=4 the value of the function is 405