Algebra practice question

Answer: 3

Slope = (11 − 5)/(4 − 1) = 6/3 = 2. Using y = 2x + b with (1, 5): 5 = 2(1) + b, so b = 3. A common slip is stopping at the slope (2) instead of solving for the intercept.

Common wrong answers

If you answered 2

That's the slope. You still need to plug a point into y = 2x + b and solve for b, which gives 3.

If you answered 5

That's the y-coordinate of the point (1, 5), not the y-intercept. The y-intercept is where x = 0, so solve 5 = 2(1) + b to get b = 3.

If you answered 0.5

You inverted the slope, computing run over rise (3/6) instead of (11 − 5)/(4 − 1) = 2.

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