Question
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If \( f(x) \) is an exponential function of the form of \( y=a b^{x} \) where \( f(4)=16 \) and \( f(4.5)=54 \), then find the value of \( f(5) \), to the nearest hundredth.

Ask by Valdez Powers. in the United States
Jan 23,2025

Real Tutor Solution

Tutor-Verified Answer

Answer

\( f(5) = 182.25 \)

Solution

Given that \( f(x) \) is an exponential function of the form \( y = ab^x \), where \( f(4) = 16 \) and \( f(4.5) = 54 \), we need to find the value of \( f(5) \) to the nearest hundredth. To find the value of \( f(5) \), we first need to determine the values of \( a \) and \( b \) using the given information. From the given information, we have: 1. \( f(4) = 16 \) 2. \( f(4.5) = 54 \) We can use these two equations to solve for \( a \) and \( b \). Let's start by using the first equation \( f(4) = 16 \) to find the value of \( a \): \[ 16 = ab^4 \] Now, let's use the second equation \( f(4.5) = 54 \) to find the value of \( b \): \[ 54 = ab^{4.5} \] We can solve these two equations simultaneously to find the values of \( a \) and \( b \). Let's solve these equations to find the values of \( a \) and \( b \) and then use them to find the value of \( f(5) \). Solve the system of equations by following steps: - step0: Solve using the substitution method: \(\left\{ \begin{array}{l}16=ab^{4}\\54=ab^{4.5}\end{array}\right.\) - step1: Calculate: \(\left\{ \begin{array}{l}16=ab^{4}\\54=ab^{\frac{9}{2}}\end{array}\right.\) - step2: Solve the equation: \(\left\{ \begin{array}{l}a=\frac{16}{b^{4}}\\54=ab^{\frac{9}{2}}\end{array}\right.\) - step3: Substitute the value of \(a:\) \(54=\frac{16}{b^{4}}\times b^{\frac{9}{2}}\) - step4: Reduce the fraction: \(54=16b^{\frac{1}{2}}\) - step5: Swap the sides: \(16b^{\frac{1}{2}}=54\) - step6: Divide both sides: \(\frac{16b^{\frac{1}{2}}}{16}=\frac{54}{16}\) - step7: Divide the numbers: \(b^{\frac{1}{2}}=\frac{27}{8}\) - step8: Raise both sides to the \(2\)-th power\(:\) \(\left(b^{\frac{1}{2}}\right)^{2}=\left(\frac{27}{8}\right)^{2}\) - step9: Evaluate the power: \(b=\frac{729}{64}\) - step10: Substitute the value of \(b:\) \(a=\frac{16}{\left(\frac{729}{64}\right)^{4}}\) - step11: Simplify: \(a=\frac{2^{28}}{729^{4}}\) - step12: Calculate: \(\left\{ \begin{array}{l}a=\frac{2^{28}}{729^{4}}\\b=\frac{729}{64}\end{array}\right.\) - step13: Check the solution: \(\left\{ \begin{array}{l}a=\frac{2^{28}}{729^{4}}\\b=\frac{729}{64}\end{array}\right.\) - step14: Rewrite: \(\left(a,b\right) = \left(\frac{2^{28}}{729^{4}},\frac{729}{64}\right)\) The solution to the system of equations is \( a = \frac{2^{28}}{729^{4}} \) and \( b = \frac{729}{64} \). Now that we have the values of \( a \) and \( b \), we can find the value of \( f(5) \) using the exponential function \( f(x) = ab^x \). Substitute the values of \( a \) and \( b \) into the function to find \( f(5) \): \[ f(5) = \frac{2^{28}}{729^{4}} \times \left(\frac{729}{64}\right)^5 \] Let's calculate the value of \( f(5) \) to the nearest hundredth. Calculate the value by following steps: - step0: Calculate: \(\frac{2^{28}}{729^{4}}\times \left(\frac{729}{64}\right)^{5}\) - step1: Evaluate the power: \(\frac{2^{28}}{729^{4}}\times \frac{729^{5}}{64^{5}}\) - step2: Rewrite the expression: \(\frac{2^{28}}{729^{4}}\times \frac{729^{5}}{2^{30}}\) - step3: Reduce the numbers: \(1\times \frac{729}{2^{2}}\) - step4: Multiply: \(\frac{729}{2^{2}}\) - step5: Evaluate the power: \(\frac{729}{4}\) The value of \( f(5) \) to the nearest hundredth is 182.25.

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Beyond the Answer

To solve for \( f(5) \), we start with the given form of the function \( f(x) = a b^{x} \) and the provided values \( f(4) = 16 \) and \( f(4.5) = 54 \). Setting up the equations with the known values: 1. From \( f(4) = 16 \): \[ a b^4 = 16 \quad (1) \] 2. From \( f(4.5) = 54 \): \[ a b^{4.5} = 54 \quad (2) \] Next, we can express \( b^{4.5} \) in terms of \( b^4 \): \[ b^{4.5} = b^4 \cdot b^{0.5} \] Substituting this into equation (2): \[ a b^4 \cdot b^{0.5} = 54 \] Now, replacing \( a b^4 \) from equation (1): \[ 16 \cdot b^{0.5} = 54 \] Solving for \( b^{0.5} \): \[ b^{0.5} = \frac{54}{16} = 3.375 \] To find \( b \), we square both sides: \[ b = (3.375)^2 = 11.390625 \] Now, substitute \( b \) back into equation (1) to find \( a \): \[ a (11.390625)^4 = 16 \] Calculating \( (11.390625)^4 \): \[ (11.390625)^4 \approx 16484.96449 \] Then, \[ a \cdot 16484.96449 = 16 \implies a = \frac{16}{16484.96449} \approx 0.000969 \] Now we can express \( f(x) \) fully: \[ f(x) = 0.000969 \cdot (11.390625)^x \] Finally, we need to find \( f(5) \): \[ f(5) = 0.000969 \cdot (11.390625)^5 \] Calculating \( (11.390625)^5 \): \[ (11.390625)^5 \approx 187384.6237 \] Then, \[ f(5) \approx 0.000969 \cdot 187384.6237 \approx 181.539 \] Thus, the value of \( f(5) \) to the nearest hundredth is: \[ \boxed{181.54} \]

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