Question

f(x) varies directly with x and f(x) equals 20 when x equals -4 what is the value of f(x) when x equals 2

Answer 1

remember that y=f(x)

direct variation y=kx

Use the given information to figure out what k is. f(x) equals 20 when x equals -4

Use calculated value of k and then answer, what is the value of f(x) when x equals 2

Answer 2

Im still confused as to how find k

Answer 3

Here is an example as well https://www.youtube.com/watch?v=3wgZugXUCGU

Answer 4

we know that y and f(x) are the same
we know that y = 20
we know that x = -4

we know that the direct variation equation is y=kx or f(x) = kx

Substitute in the values above and then solve for k.

Answer 5

20 = k(-4)?

Answer 6

yes now solve for k

Answer 7

-2/5?

Answer 8

No, isolate k by dividing both sides by -4.

Answer 9

-5 = k?

Answer 10

@ajspeller

Answer 11

Yes.

y=kx

y=(-5)x

No substitute in the value of x, 2, which is given and then solve for y. This is will be the answer to the question.

Answer 12

-10

Answer 13

Yes

Answer 14

thank you!

Answer 15

no problem