Question

On which of the following intervals is the function f(x) = 4 cos(2x − π) decreasing?

Answer 1

x = pi over 2 to x = π

x = 0 to x = pi over 2

x = pi over 2 to x = 3 pi over 2

x = π to x = 3 pi over 2

Answer 2

@primeralph @dan815 @Destinymasha

Answer 3

@paki

Answer 4

If you're expected to solve this graphically, then you can use this program to help:
https://www.desmos.com/calculator/pck1ifiyez

If you're expected to solve algebraically, then just plug in x-values along each interval.

Answer 5

This graph might be more useful to you:
https://www.desmos.com/calculator/lzigif6b0b

Answer 6

Yes. I'm looking at all of the intervals and all of them show values increasing.

Answer 7

The graph begins to decreasing finally after 3pi/2 and no interval starts with that

Answer 8

Make sure to check each interval. You only want the range of x values where it is decreasing along the entire interval.

Answer 9

I just looked at the 2nd graph you sent and I found it.

Answer 10

Thanks.