If y varies directly as the x^2 and y = 200 when x = 5, what is the value of y when x = -3? a. -72 b. 120 c. 72 d. -120 Please select the best answer from the choices provided

Question

asked Aug 25, 2019 60.2k views

1 Answer

Marin Takanov · Answer 1 · 2019-09-01T10:31:40+0000

As the variation is direct we have:

y = kx ^ 2

We must find the value of k.
For this, we use the following data:
y = 200 when x = 5
Substituting values we have:

200 = k5 ^ 2

Clearing k:

k = 200/5 ^ 2 k = 200/25 k = 8

Then, the function is:

y = 8x ^ 2

We evaluate the function for x = -3

y = 8 (-3) ^ 2 y = 8 (9) y = 72

Answer:
the value of y when x = -3 is:
c.
72