contestada

If y varies directly as x^2 and y = 144 when x = 4, what is the value of y when x = -5?
a.
-225
b.
225
c.
180
d.
-180


Please select the best answer from the choices provided

Respuesta :

carlosego
As the variation is direct then we have the following expression:
 [tex]y = kx ^ 2 [/tex]
 From here, we clear the value of k.
 For this we use the following data:
 y = 144 when x = 4
 Substituting values:
 [tex]144 = k4 ^ 2 [/tex]
 Clearing k we have:
 [tex]k = 144/4 ^ 2 k = 144/16 k = 9[/tex]
 Then, the function is:
 [tex]y = 9x ^ 2 [/tex]
 When x = -5 we have:
 [tex]y = 9 (-5) ^ 2 y = 9 (25) Y = 225[/tex]
 Answer:
 the value of y when x = -5 is:
 b.
 225

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