SOLUTION: define variables and write an equation to model the relationship in the table payment change

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Question 764747: define variables and write an equation to model the relationship in the table
payment change
$1 $9
$2 $8
$3 $7

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
payment change
$1+ $9
$2+ $8
$3 $7
if payment represents x and change y, we have points (1,9),(2,8),(3,7) that should lie on same line; so, we can fine a line passing through two points:

Solved by pluggable solver: Find the equation of line going through points
hahaWe are trying to find equation of form y=ax+b, where a is slope, and b is intercept, which passes through points (x1, y1) = (1, 9) and (x2, y2) = (2, 8).
Slope a is a+=+%28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29+=+%288-9%29%2F%282-1%29+=+-1.
Intercept is found from equation a%2Ax%5B1%5D%2Bb+=+y%5B1%5D, or -1%2A1+%2Bb+=+10. From that,
intercept b is b=y%5B1%5D-a%2Ax%5B1%5D, or b=9--1%2A1+=+10.

y=(-1)x + (10)

Your graph:




so, equation is y=-x%2B10
now we can check if all three points lie on this line: