Question

Determine the values of x for which the function f is decreasing, where
f(x)=(440−x)^(2)+x^(2)
enter your answer in interval notation
use your answer to determine which is bigger, 154^(2) + 286^(2) or 198^(2) + 242^(2)

Answer 1

take the derivative to get
f'(x) = 2(440 - x)(-1) + 2x = -880 + 4x.

Find the zeros of the derivative to get x = 220. your intervals are (-inf, 220), (220, inf). pick a value in these intervals and plug in to the derivative, if negative, f is decreasing. if positive, f is increasing.

Answer 2

find the zeros?

Answer 3

solve for 0
ie -880+4x=0

Answer 4

Actually it was done for you 220

Answer 5

Pick a number from the intervals, and test it to see if it is positive or negative

Answer 6

i plug the number into 4x-880?