contestada

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

Respuesta :

carlosego
As the variation is direct we have:
 [tex]y = kx ^ 2 [/tex]
 We must find the value of k.
 For this, we use the following data:
 y = 200 when x = 5
 Substituting values we have:
 [tex]200 = k5 ^ 2 [/tex]
 Clearing k:
 [tex]k = 200/5 ^ 2 k = 200/25 k = 8[/tex]
 Then, the function is:
 [tex]y = 8x ^ 2 [/tex]
 We evaluate the function for x = -3
 [tex]y = 8 (-3) ^ 2 y = 8 (9) y = 72[/tex]
 Answer:
 the value of y when x = -3 is:
 c.
 72

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