Finding an equation of an Exponential Function from a Graph

• September 23rd 2008, 02:37 PM
zodiacbrave
Finding an equation of an Exponential Function from a Graph
Hello, there's a graph in my textbook. that appears to start at (0,0) and the only given point is (1,2) and there is a horizontal asymptote at y = 4.

The question asks to give a possible formula for the function.

The equation is increasing from left to right, but it concaves down from (0,0) to oo.

My question is, how am I supposed to find a formula from the given information? thank you
• September 23rd 2008, 06:41 PM
skeeter
try this one ...

$y = 4(1 - 2^{-x})$
• September 23rd 2008, 07:09 PM
zodiacbrave
I think the answer is -(2)^-(x-2)+4 but i just can't seem to prove how i got it. I just don't understand how I'm supposed to find an equation based solely on a graph