a) You have the following function:
f(x) = 5x³ - 1
In order to determine which is the value of the function for x = 2, you replace by 2 where x is into the fucntion, just as follow:
f(2) = 5(2)³ - 1 Next, you make the operations
f(2) = 5(8) - 1
f(2) = 40 - 1
f(2) = 39
Hence, the value of the function for x=2 is f(2) = 39
b)
f(x) = 7x² - 28
f(2) = 7(2)² - 28 = 7(4) - 28 = 28 - 28 = 0
c) By the form of the line you can conclude that the value of the function for x=6 is f(6) = -2