AlgebraVery hardConstant making two lines meet on the x-axis
Algebra practice question
In the xy-plane, the lines y = 2x + b and y = −x + 7, where b is a constant, intersect at a point on the x-axis. What is the value of b?
Answer: -14
The second line meets the x-axis at (7, 0). For the first line to pass through it: 0 = 14 + b, so b = −14.
Common wrong answers
- If you answered 7
- 7 is the x-coordinate of the meeting point.
- If you answered 14
- 14 has the sign wrong.
- If you answered -7
- −7 uses y = x + b.
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