AlgebraMediumZero of a linear function from two points
Algebra practice question
The graph of the linear function f in the xy-plane passes through the points (0, −2) and (4, 6). For what value of x is f(x) = 0?
Answer: 1
Slope: (6 − (−2))/(4 − 0) = 2, and f(0) = −2, so f(x) = 2x − 2. Set 2x − 2 = 0: x = 1.
Common wrong answers
- If you answered 2
- 2 is the slope, or 2x at the zero; the zero itself is x = 1.
- If you answered -2
- −2 is f(0), the y-intercept — where the graph crosses the y-axis, not the x-axis.
- If you answered -1
- −1 has the wrong sign: 2x = 2 gives x = 1.
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