The first and 3rd choices are just sin and cos waves, with amplitude of 1 .
So it has to be the 2nd or 4th choice.
The y-intercept is the point on the graph where x=0.
So if the y-intercept is -1, that just means that f(0)=-1 .
So let's test the two choices:
f(x) = -2 sin(x) - 1
f(0) = -2 sin(0) - 1
sin(0) = 0 so
f(0) = -2 (0) - 1 .
That looks like it works.
Just to be sure, let's check the other possible choice.
f(x) = -2 cos(x) - 1
f(0) = -2 cos(0) - 1
cos(0) = 1 so f(0) = -2 (1) - 1 = -3 .
Beautiful ! The y-intercept of choice-2 is -1,
and the y-intercept of choice-4 is -3. The answer is choice-2.
