AlgebraMediumVertical gap between two parallel lines
Algebra practice question
In the xy-plane, the lines y = 2x + 1 and y = 2x − 7 are parallel. For any value of x, how many units is the point on the first line directly above the point on the second line?
Answer: 8
At any x, the difference in y is (2x + 1) − (2x − 7) = 8.
Common wrong answers
- If you answered 2
- 2 is the common slope, not the gap.
- If you answered 6
- 6 is 7 − 1, mishandling the sign of −7.
- If you answered -8
- −8 has the wrong sign; the first line is above the second.
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