Question 30872: write an equation that represents the data in the table.
x|0|-2|-4|-6|-8
y|-4|-10|-16|-22|-28
Answer by longjonsilver(2297)   (Show Source):
You can put this solution on YOUR website! there are 5 terms here, numbered 1,2,3,4 and 5.
Look at the difference between the x-terms... a difference of 2, well -2 to be exact.
And look at the difference between the y-values: 6... well -6 to be exact.
This is a "three-times table" since as one variable changes, the other changes by 3 times that. So we have y=3x.
Now, y=3x is THE 3-times table ie 3,6,9,12,15,18, etc. We have another 3-times table, "shifted" from this. To find the shift, we need to just pick one value of x, so pick an easy one. Namely x=0.
when x=0, y=3x becomes y=0 too. We need y to be -4, so we need to subtract 4 from 0 to get the -4.
So, the equation is y=3x-4
Now check with a value away from the x=0 value we picked. So, lets pick x=-8.
When x=-8, y=3x-4 becomes
y = 3(-8) -4
y = -24-4
y = -28 which is the correct value.
So, y=3x-4 is the correct equation of this set of coordinates.
jon.
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