AlgebraVery hardx-intercept of a line through two points
Algebra practice question
In the xy-plane, a line passes through (2, 3) and (4, −1). What is the x-coordinate of the point where the line crosses the x-axis?
Answer: 3.5 or 7/2
Slope: (−1 − 3)/(4 − 2) = −2. Equation: y − 3 = −2(x − 2), so y = −2x + 7. Set y = 0: x = 3.5.
Common wrong answers
- If you answered 3
- 3 is the y-coordinate of the first point, not the x-intercept.
- If you answered 7
- 7 is the y-intercept, not the x-intercept.
- If you answered -3.5
- −3.5 has the wrong sign.
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