Question

Suppose y varies directly with x. Write an equation if y=-4 when x=2.

Answer 1

Answer: The formula for direct variation is y = kx. To find k, divide y by x. K = -2. The equation is y = -2x

Explanation:

Step 1) find k using formula, which is y= kx.

y = kx. (Plug in -4 for y and 2 for x)

-4 = k(2) (Divide by 2 on both sides)

-4/2 = k

-2 = k. So k = -2

*Just FYI, “k” is the constant of variation.

Step 2) plug in k to the formula, which is y = kx.

y = kx

y = -2x

So the equation is: y = -2x

You’re done! Hope this helped and good luck with your work!

Answer 2

y=8x-20

Explanation:

When you plug in the given variables (y=-4 & x=2) and solve you get the right answer.

Ways to check:

-4=8x-20 and solve for x

-or-

y=8(2)-20 and solve for y