Find the value of the function y = 3x power 2 - 21 when x = 4

To find the value of the function when x = 4, we substitute x = 4 into the equation:

y = 3x^2 - 21
y = 3(4)^2 - 21
y = 3(16) - 21
y = 48 - 21
y = 27

Therefore, when x = 4, the value of the function y = 3x^2 - 21 is 27.