Answer:
[tex]y = 4*5^x[/tex]
Step-by-step explanation:
Given
[tex](x_1,y_1) = (-3,\frac{4}{125})[/tex]
[tex](x_2,y_2) = (1,20)[/tex]
Required
Determine the exponential equation
An exponential equation is of the form: [tex]y = ab^x[/tex]
In: [tex](x_2,y_2) = (1,20)[/tex]
[tex]20 = ab^1[/tex]
[tex]20 = ab[/tex] ---- (1)
In: [tex](x_1,y_1) = (-3,\frac{4}{125})[/tex]
[tex]\frac{4}{125} = ab^{-3}[/tex] --- (2)
Divide (1) by (2)
[tex]20/\frac{4}{125} = \frac{ab}{ab^{-3}}[/tex]
[tex]20/\frac{4}{125} = b^4[/tex]
[tex]20*\frac{125}{4} = b^4[/tex]
[tex]5*125 = b^4[/tex]
[tex]625 = b^4[/tex]
Take 4th roots of both sides
[tex]\sqrt[4]{625} = b[/tex]
[tex]5 = b[/tex]
[tex]b = 5[/tex]
Substitute [tex]b = 5[/tex] in [tex]20 = ab[/tex]
[tex]20 = a * 5[/tex]
Solve for a
[tex]a = 20/5[/tex]
[tex]a = 4[/tex]
Hence, the equation is:
[tex]y = 4*5^x[/tex]
