Writing an Equation of a Line Determine the equation of a line and/or graph a linear equation.
Slope-intercept Form y = mx + b any ordered pair (x,y) Slope-intercept Form y = mx + b Slope y-intercept
The method used to write an equation of a line depends on the information about the line that is available.
If given the slope and y-intercept, slope-intercept form. Example m = 5, b = 7 5 7 y = ___ x + ___
If given a point and the slope, Example m = –2, contains (5, –8) Step 1 Substitute –2 for m, 5 for x, and –8 for y; then simplify to find the value of b. y = mx + b –8 = –2(5) + b –8 = –10 + b 2 = b Step 2 Substitute –2 for m, and 2 for b. y = –2x + 2
If given two points, First, find the slope using the slope formula. Example contains (5, –8) and (2, 7) m = 15 –3 m = –5 m = 7 – -8 2 – 5
If given two points, continued Then use the slope you just found and EITHER point to work like the previous example. y = -5x + b 7 = -5 (2) +b 7 = -10 + b 17 = b m = –5, contains (5, –8) and (2, 7) y = –5x + 17
Parallel lines
you try Find the equation of each line using the given information. m=2, y-intercept is -1 the line passes through the points (8, 2) and (12, 4) the line is parallel to the line y = ⅔x + 4, and passes through the points (6, 7)