Question

If f(x) varies directly with x^2, and f(x) = 75 when x = 5, find the value of f(8).
(I can find the answer but I need help putting the equation together)

A. 192


B. 25


C. 256


D. 40

Answer 1

@Compassionate @Luigi0210

Answer 2

Varies directly meaning it would look something like this: \(\ y=kx \)

Answer 3

In your case, it would be \(\large f(x)=kx^2\)

Answer 4

what does k stand for again?

Answer 5

constant something I think?

Answer 6

Yes, it's the constant you're solving for in the equation.

Answer 7

so its 75=k5^2?

Answer 8

Once you plug in all the information given \(\large 75 = k (5)^2 \)

You solve for "k"

Once you get k you can plug it back in with the new condition \(\large f(8) \)

Answer 9

so then it becomes f(8)=3x^2?

Answer 10

or is the x still 5?

Answer 11

* \(\large f(x)=3x^2 \)

But yes, then you just plug in "8" for "x" as \(f(8) \) dictates.

\(\large f(8)=3 (8)^2 \) and that will give you your solution (:

Answer 12

ohh okay thanks a bunch!

Answer 13

No prob :P

Answer 14

i got 192

Answer 15

You would be correct.

Answer 16

Yes!