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Write an exponential function that goes through the points (5, 5) and (8, 135).

Sagot :

Sure, let's find the exponential function that passes through the points (5, 5) and (8, 135).

An exponential function can be written in the form:
[tex]\[ y = a \cdot b^x \][/tex]

To find the values of [tex]\(a\)[/tex] and [tex]\(b\)[/tex], we can use the given points (5, 5) and (8, 135).

First, rewrite the function for the two points:
1. For (5, 5):
[tex]\[ 5 = a \cdot b^5 \][/tex]

2. For (8, 135):
[tex]\[ 135 = a \cdot b^8 \][/tex]

Now, we have two equations:
[tex]\[ \begin{cases} 5 = a \cdot b^5 \\ 135 = a \cdot b^8 \end{cases} \][/tex]

To solve for [tex]\(a\)[/tex] and [tex]\(b\)[/tex], divide the second equation by the first to eliminate [tex]\(a\)[/tex]:

[tex]\[ \frac{135}{5} = \frac{a \cdot b^8}{a \cdot b^5} \][/tex]

Simplify the right-hand side:

[tex]\[ 27 = b^{8-5} \\ 27 = b^3 \\ \][/tex]

Now, solve for [tex]\(b\)[/tex]:

[tex]\[ b = \sqrt[3]{27} \\ b = 3 \][/tex]

With [tex]\(b\)[/tex] known, substitute [tex]\(b\)[/tex] back into one of the original equations to solve for [tex]\(a\)[/tex]:

Using [tex]\(5 = a \cdot 3^5\)[/tex]:
[tex]\[ 5 = a \cdot 243 \\ a = \frac{5}{243} \\ a \approx 0.0205761 \][/tex]

So, the values are:
[tex]\[ a \approx 0.0205761 \\ b = 3 \][/tex]

Thus, the exponential function that passes through the points (5, 5) and (8, 135) is:
[tex]\[ y = 0.0205761 \cdot 3^x \][/tex]