CPM Homework Help : GB8I Problem 8-111

Use the graph below to write a possible equation in $y = ab^x$ form.
Decreasing exponential graph, x axis is horizontal asymptote, with y-intercept at (0, comma 1), & slope triangle, from y-intercept, labeled as follows: vertical leg, negative 0.5, horizontal leg, + 1.

Hint:

What is the value of $a$ , when $x = 0$ ?

More help:

What is the multiplier ( $b$ )? Substitute $(x, y)$ from a different point, and solve for $b$ .