If y varies directly as x^2 and y = 144 when x = 4, what is the value of y when x = -5?

1 answer:

6 0

As the variation is direct then we have the following expression:
$y = kx ^ 2
$
From here, we clear the value of k.
For this we use the following data:
y = 144 when x = 4
Substituting values:
$144 = k4 ^ 2
$
Clearing k we have:
$k = 144/4 ^ 2

k = 144/16

k = 9$
Then, the function is:
$y = 9x ^ 2
$
When x = -5 we have:
$y = 9 (-5) ^ 2

y = 9 (25)

Y = 225$
Answer:
the value of y when x = -5 is:
b.
225

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