AlgebraHardSlope that makes two lines meet on the x-axis
Algebra practice question
In the xy-plane, the lines 2x + 3y = 12 and y = mx + 1 intersect at a point on the x-axis, where m is a constant. What is the value of m?
Answer: -1/6
The first line meets the x-axis where y = 0: 2x = 12, x = 6. The point (6, 0) must be on y = mx + 1: 0 = 6m + 1, so m = −1/6.
Common wrong answers
- If you answered 1/6
- 1/6 has the wrong sign: 6m = −1.
- If you answered -2/3
- −2/3 is the slope of the first line, not m.
- If you answered -1/4
- −1/4 comes from using the y-intercept 4 instead of the x-intercept 6.
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