### Home > CCA2 > Chapter 7 > Lesson 7.2.1 > Problem7-121

7-121.

Find the equation of the exponential function of the form $y = ab^{x}$ that passes through each of the following pairs of points.

1. $\left(1,18\right)\ \text{and}\ \left(4,3888\right)$

Construct two equations by substituting the coordinates
for $x\ \text{and}\ y$.

$18 = ab^{1}$
$3888 = ab^{4}$

Use substitution to find the value of $a$ and $b$.

$a = \frac{18}{b}$

$3888 = \frac{18}{b}b^4$

$y = 3\left(6\right)^{x}$

2. $\left(-2,-8\right)\ \text{and}\ \left(3,-0.25\right)$

Use the same method as part (a).