### Home > CCA > Chapter 7 > Lesson 7.2.1 > Problem 7-87

7-87.

Find a possible exponential function in

*y*=*a · b*form that represents each situation described below. Homework Help ✎^{x}Has an initial value of 2 and passes through the point (3, 128).

Passes through the points (0, 4) and (2, 1).

Since it has an initial value of 2, the value of *a* is 2. Substitute this into the general equation *y* = *ab ^{x}*.

Substitute the values 3 for *x* and 128 for *y*, then solve for *b*.

Create two equations substituting the values of the ordered pairs for *x* and *y* into the equation *y* = *ab ^{x}*.

Solve the system of equations for *a* and *b*.

Be sure you use your results for *a* and *b* to write the equation.