Write the exponential equation that contains the points (−2,4)

(

2
,
4
)
and (3,972)
(
3
,
972
)
.(1 point)
The equation is $$y=·.

1 answer

To find the exponential equation that passes through the points \((-2, 4)\) and \((3, 972)\), we can assume the general form of the exponential equation is:

\[ y = ab^x \]

where \(a\) is the initial value (the value of \(y\) when \(x = 0\)) and \(b\) is the growth factor.

We can create two equations using the given points:

  1. For the point \((-2, 4)\): \[ 4 = ab^{-2} \]

  2. For the point \((3, 972)\): \[ 972 = ab^{3} \]

Now we have a system of two equations:

  1. \(4 = \frac{a}{b^2}\)
  2. \(972 = ab^3\)

From the first equation, we can express \(a\) in terms of \(b\): \[ a = 4b^2 \]

Now, substitute this expression for \(a\) into the second equation: \[ 972 = (4b^2)b^3 \] \[ 972 = 4b^{5} \]

Now, solve for \(b\): \[ b^5 = \frac{972}{4} = 243 \]

To solve for \(b\), take the fifth root of \(243\): \[ b = 243^{1/5} = 3 \]

Now that we have \(b\), we can find \(a\) using \(a = 4b^2\): \[ a = 4(3^2) = 4 \times 9 = 36 \]

Now we have both \(a\) and \(b\): \[ a = 36, \quad b = 3 \]

So, the exponential equation that contains the points \((-2, 4)\) and \((3, 972)\) is: \[ y = 36 \cdot 3^x \]

The final equation is: \[ \boxed{y = 36 \cdot 3^x} \]