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When drawing a straight-line rule by working out points, two points are enough to draw the line. Why is a third point still worth working out?
AIt makes the line reach further across
BIf it misses the line, a slip has been made
CIt fixes the place where the line starts
DIt turns the line into a smooth curve
Answer & Solution
Correct answer: B. If it misses the line, a slip has been made
1. Any two points can be joined by a straight line, whether or not the working behind them was right.
2. A third point worked out from the same rule must land on that same line.
3. If it lands off the line, one of the three sums must be wrong.
4. So the third point is a check on the arithmetic, option B.
_Source: OpenStax College Algebra (CC BY 4.0), Ch 4 "Linear Functions", section 4.1 Linear Functions_
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