Mathematics: If f(x) varies directly with x^2, and f(x) = 75 when x = 5, find the value of f(8). 192 256 25 40

I m pretty sure the answer is 4 because, 4*21= 84....

If f(x) varies directly with x^2, and f(x) = 75

NEONREDBLADE

10.03.2022

The correct answer option is 192.

Step-by-step explanation:

We know that f(x) varies directly with $x^{2}$ so we can write it as:

f(x) ∝ $x^{2}$

Changing it to an equality by the addition of a constant :

$f(x) = k.x^{2}$

If f(x) = 75 when x = 5, then we can find the value of k:

75=k(5)^2

$k=\frac{75}{25} =3$

If k = 3, we can find the value of f(8):

f(8)=3(8)^2

f(8)=3*64

f(8)= 192

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