Chapter 1 Linear Functions Section 1.1 Slopes and Equations of Lines The Coordinate Plane Slope of a Line Finding the Intercepts of an Equation To find the y-intercept of an equation of a line, substitute zero for x and solve for y. To find the x-intercept of an equation of a line, substitute zero for y and solve for x. Example: Find the x-and y-intercept of the line represented by 3x - 4y = -12. Slope of a Line Example 1 Find the slope of the line that passes through a.) (-4, -3) and (2, -7). b.) (5, 8) and (-1, 8) c.) (12, -2) and (12, -9) Special Cases of Slope The slope of a horizontal line is zero. The slope of a vertical line is undefined. Equations of a Line An equation in two first-degree variables has a line as its graph and is called a linear equation. The standard form of the equation of a line is Ax + By = C. Slope-Intercept Form Example 2 Find the equation of the line having a slope of -3/5 and a y-intercept of (0, -1). Point-Slope Form Example 3 Find the equation of the line that passes through (-3, 1) and (-2, -4). Write the answer in slope-intercept form. Equations of Lines Perpendicular and Parallel Lines Example 4 Write the equation of the line that passes through (-1, -4) and is parallel to 4x + 2y = 10. Write the equation of the line that passes through (7, 3) and is perpendicular to y = 3x -1. Example 5 Write the equation of the line that is parallel to y = 10 and passes through (5, 8). Write the equation of the line that is perpendicular to x = -3 and passes through (-4, -1).