# algebra

posted by
**Viggo** on
.

How do you do this:

Write an exponential function of the form y=ab^x that has a graph through (-2, 25) and (1, 10).

This is what I have so far:

10=ab^1

10/b=a

y=10/b*b^x

2/25=10b^-3

.008=b^-3

Then I am stuck. Am I doing it right so far? How do I continue? Thanks!

I don't get your second last line, I had:

25 = (10/b)b^-2

2.5 = b^-3

0.4 = b^3

b=cuberoot(.4)=.7368...

then a=10/.7368... = 13.572..

so y = 13.572(.7368)^x

I checked both data values, they work

gotcha thanks