 Writing an Equation of a Line

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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 = 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)

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