Answer: choice C, y = 0.014x+0.85
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Explanation:
Each column of the table represents an (x,y) pair of values
x = number of pages
y = cost
If we look at the first two columns, we see the two points (50,1.55) and (100,2.25). The x value is listed first. Let's compute the slope of the line through these two points
m = (y2-y1)/(x2-x1)
m = (2.25-1.55)/(100-50)
m = 0.7/50
m = 0.014
So far, we see the answer is between A,B or C as they have the slope of 0.014
Use this slope value, and one of the points -- say (x,y) = (50,1.55) -- to find the y intercept b
y = mx+b
y = 0.014x+b .... plug in the slope found earlier
1.55 = 0.014*50+b ... plug in the point (x,y) = (50,1.55)
1.55 = 0.7+b
1.55-0.7 = 0.7+b-0.7 ... subtract 0.7 from both sides
0.85 = b
b = 0.85
With m = 0.014 as the slope and b = 0.85 as the y intercept, we can say that y = mx+b turns into y = 0.014x+0.85. That narrows the answer down to choice C.
