Algebra practice question

Answer: -2 or −2

A slope of −2 and y-intercept 4 give f(x) = −2x + 4. Then f(3) = −6 + 4 = −2.

Common wrong answers

If you answered 2

2 is 4 − 2, subtracting the slope once instead of 3 times. f(3) = 4 − 2 × 3.

If you answered 10

10 is 2(3) + 4, using a slope of +2. The slope is −2, so the function falls as x grows.

If you answered -6

−6 is −2 × 3 without the y-intercept. Add the 4: −6 + 4 = −2.

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