Answer:
Variation equation: y = k/√x
constant of variation: 200
Variation Equation by plugging the value of k: y = 200/√x
Step-by-step explanation:
If y varies inversely with the SQUARE ROOT of x, then;
y = k/√x
If x = 4, y = 100.
100 = k/√4
100 = k/2
200 = k
k = 200
Substitute into the expression
y = k/√x
y = 200/√x
The answer is: A - f(x) = 1/2 cos (x)
Answer:
B
Step-by-step explanation:
The best - well, only way- is to check a few points.
Namely -1 (unless your eyesight is really poor!), 0, 1, 2, and 3.

Now you can mark all these points in each graph (well, you could if they were on paper and not on a screen) and see which one of the lines passes through all of them. Spoiler alert, it's the B graph.
A represents
, B is the one you want, C is
and D looks like 