Problem 4 - Entrance Test

What is the equation of the line that passes through points (2, 3) and (4, 5) ?

A. y = x + 1B. y = x - 1C. y = 2x + 1D. y = x/2 + 3

Correct: A

First, find the slope of the line (y2 - y1)/(x2 - x1) = (5 - 3)/(4 - 2) = 2/2 = 1. The slope is 1. Now use point-slope form y - y1 = m(x - x1). Use point (2, 3) and m = 1. y - 3 = 1(x - 2), y - 3 = x - 2, y = x + 1.