Question

Write a direct variation equation that relates x and y. Assume that y varies directly as x. Then solve.

If y = –49 when x = –7, find x when y = –7.

Answer 1

Direct variation can be written in the form y=kx. Plug in what you're given and solve for k. (that will be your constant.) The problem will be -49=-7k.

Answer 2

choices were a.
y = 7x; –1
c.
y = –7x; 1
b.
y = 7x; –0.9
d.
y = 6x; –1

Answer 3

What did you get for k when you solved the equation above (-49=-7k)?

Answer 4

To get k, divide both sides by (-7)

Answer 5

y = –7x; 1

Answer 6

If you divide -49 by -7, what do you get. That is k, the constant. Stay with me through 1 more step please.

Answer 7

ok its positive 7

Answer 8

right, so when you plug 7 in for k when y is -7, you get -7=7x. That gives your answer for x when y = -7. Do you get it?

Answer 9

y = 7x; –1

Answer 10

right!

Answer 11

thanks

Answer 12

you"re welcome!