The temperature of a chemical compound, in degrees Celsius, changes when the compound is exposed to UV light. The table below shows the temperature of the compound, in degrees Celsius, x minutes after the compound is exposed to UV light.
x
0
2
4
6
8
f(x)
15
15.5
17
19.5
23

Write the quadratic function that corresponds to the given table of values in standard form, f(x) = ax2 + bx + c, where a, b and c are constants.