solve c(x)=x^2-40x+405 where x equals 15

just replace x with 15 and do the arithmetic.

c(15) = 15^2 - 40(15) + 405
= .....

To solve the equation c(x) = x^2 - 40x + 405 when x = 15, we can substitute the value of x into the equation and calculate the result.

First, let's substitute the value of x into the equation:

c(15) = 15^2 - 40(15) + 405

Now, we can simplify the calculation:

c(15) = 225 - 600 + 405

Next, we simplify further:

c(15) = 405 - 600 + 405

Now, we can combine like terms:

c(15) = -195 + 405

Finally, we calculate the result:

c(15) = 210

Therefore, when x = 15, c(x) is equal to 210.