Determine a relationship between x- and y-values. Write an equation.

{(1, -1), ( 2, -2), (3, -3), (4, -4)

mmmhhh

did you notice that the y is always the negative of the x ???

so .....

Is the answer y = -x, then?

x=-y

so that would be the general expresion

or even better you could say that x+y=0

Algebra teachers like it more :)

Are you certain?

jason wants to buy his brother a comic book. If he buys it online it costs $3.50, but if he buys it in the store there is a 20% markup. How much does the comic book cost in the store?

y = -x