We have a function of the form:
![y = A * b ^ t](https://img.qammunity.org/2019/formulas/mathematics/middle-school/649tq65ipqbq8smwoekvgx187kgf42ba2i.png)
Where,
A: initial height
b: growth rate
We must find the values of A and b.
For this we use the following data:
After 10 days, the plant is 25 centimeters tall:
![25 = A * b ^ {10}](https://img.qammunity.org/2019/formulas/mathematics/middle-school/xb2zmz7rc1zs79srwb4ouzxv1xnpdvusop.png)
After 20 days, the plant is 45 centimeters tall
![45 = A * b ^ {20}](https://img.qammunity.org/2019/formulas/mathematics/middle-school/t0zrk5zwg0rzico7zibi55p99ccwjtykok.png)
We observe that we have a system of equations where there are:
2 equations
2 unknowns
Solving the system we have:
![A = 13.9 b = 1.06](https://img.qammunity.org/2019/formulas/mathematics/middle-school/g4fixt9vqwu2mzifse3p8h2oh9nz91dszf.png)
Thus, substituting values, we have that the equation that models the problem is:
Answer:
An equation that models the height of the plant, and, after x days is:
![y = 13.9 * 1.06 ^ t](https://img.qammunity.org/2019/formulas/mathematics/middle-school/cmb5k2meabdufp0h59luyc3c80vl183dvb.png)