Question #b310b

1 Answer
sente
Oct 9, 2016

(x, y) = (x, x-90)

Explanation:

Given two variables, at least two equations are needed to determine two unique values for those variables. With only a single equation, we are showing a relationship between the two variables which may be fulfilled by many (x, y) pairs.

In the given example, we have x-y = 90

=> x - y + y - 90 = 90 + y - 90

=> y = x - 90

Thus, for any x value, we can find a corresponding y value which fulfills x-y=90 by setting y=x-90. If we graph this, we get a line, every point of which is an (x, y) pair satisfying our equation:

graph{x-90 [-275, 333, -168, 136]}

Example (x,y) pairs:
(-10, -100)
(0, -90)
(1, -89)
(10, -80)
(90, 0)
(100, 10)

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