Respuesta :
Answer: [tex]7.93[/tex]
Step-by-step explanation:
Given
[tex]f(x)[/tex] is an exponential function. Suppose [tex]f(x)[/tex] is [tex]ae^{bx}[/tex]
[tex]f(1.5)=5\ \text{and}\ f(7.5)=79[/tex]
[tex]\Rightarrow 5=ae^{1.5b}\\\Rightarrow \ln 5=\ln a-1.5b\quad \ldots(i)[/tex]
Similarly,
[tex]\Rightarrow 79=ae^{7.5b}\\\Rightarrow \ln(79)=\ln a+7.5b\quad \ldots(ii)[/tex]
Subtract (i) and (ii)
[tex]\Rightarrow \ln (79)-\ln (5)=9b\\\Rightarrow \ln (\frac{79}{5})=9b\\\\\Rightarrow b=\dfrac{\ln (\frac{79}{5})}{9}\\\\\Rightarrow b=0.3066[/tex]
Insert the value of [tex]b[/tex]
[tex]\Rightarrow 5=ae^{0.46}\\\Rightarrow a=5\times 0.6312\\\Rightarrow a=3.156\approx 3.16[/tex]
So, the function becomes
[tex]\Rightarrow f(x)=3.16e^{0.3066b}[/tex]
[tex]\Rightarrow f(3)=3.16e^{0.3066\times 3}\\\Rightarrow f(3)=7.927\approx 7.93[/tex]
Answer:
7.93
General Exponential Form: y=ab^x
Plug in both points
divide the equations
cancel out a, subtract exponent of b
