Question

Find the range of y = 3cos4x - 2.

-5 ≤ y ≤ 5
-5 ≤ y ≤ 1
-3 ≤ y ≤ 3
1 ≤ y ≤ 3

Answer 1

-5 ≤ y ≤ 1

Explanation:

correct

Answer 2

`- 5\leqslant y \leqslant 1`

EXPLANATION

The given cosine function is:

`y = 3 \cos4x - 2`

The amplitude of this function is:

3

This means the parent function has range:

`- 3 \leqslant y \leqslant 3`

The given function has been shifted down by 2 units.

So we add -2 to the peak values to get

`- 2 + - 3 \leqslant y \leqslant 3 + - 2`

The given function has range:

`- 5\leqslant y \leqslant 1`