Find Equation of Exponential Function given two points that it passes through

In this example, we are given two points that an exponential function passes through. Neither is the y-intercept. We substitute them into the general form for an exponential function to create two equations. We then walk through the substitution method for solving systems of equations by solving one of the equations for one of the variable. The result is then substituted into the other equation. The resulting equation will then only contain one variable so we solve for the remaining variable. This result is then substituted back into the first step to solve for the remaining unknown variable.

[teambrinatv]

I spent hours stuck on trying to understand this math and you made it so easy! Thank you so much, right on time for my math midterm tomorrow.

[Ridha]

near the end, isn't b supposedto be (1+r)^x? but you just place 2 in there without the 1+