# 2.4 Write Equations of Lines

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2.4 Write Equations of Lines
Date: 9/4 Objective: Use point slope formula to write and equation of a line.

Slope Intercept Form: y = mx + b
Point Slope Formula: y – y1 = m(x – x1) If Given a slope m and a point (x1 , y1 ), then use point slope formula to write an equation of a line that passes through the point using that slope. If Given (x1 , y1) and (x2 , y2 ) then you must find the slope first using the slope formula, then use the point slope formula to write the equation of the line.

Example: Write an equation when given the slope and y-intercept. m = ¾
b = -2

Write an equation when given the slope and a point.
Write an equation of a line that passes through (5,4) and has a slope of -3.

Write an equation of a line when given two points.
Write an equation of a line that passes through the points (5,-2) and (2,10). 1st: Use slope formula to find (m = ) 2nd: Use point slope formula

Write equations of parallel or perpendicular lines.
Write an equation of the line that passes through (-2,3) and is (a) parallel to and (b) perpendicular to, the line y = -4x + 1.