Question

If f(x) varies directly with x2, and f(x) = 75 when x = 5, find the value of f(4).

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Answer 1

so... what would your equation be?

Answer 2

f(x) = kx

Answer 3

@Nnesha Could you help?

Answer 4

f(x) varies directly with x^2

not just x

Answer 5

try again @Bananas1234

Answer 6

try again for what? the formula?

Answer 7

yes, it's not f(x) = kx

Answer 8

its the direct variation formula right?

Answer 9

yeah but you are missing something

Answer 10

then it is k = f(x)/x to find the constant.

Answer 11

it's not that either

Answer 12

f(x) varies directly with x^2

f(x) varies directly with x SQUARED

Answer 13

oh sorry i didn't know what you meant

Answer 14

so what is the true formula here?

Answer 15

f(x) = kx^2

Answer 16

correct

Answer 17

we're given that x = 5 and f(x) = 75. Use them both to find k

Answer 18

k = 75/5? that would = 15. so does k = 15?

Answer 19

remember, we have x^2 and not just x

Answer 20

/5