2.5 1

Section 2.5Other Equations of Lines

Point-Slope Form (y – y1)=m(x – x1) Special pairs of lines:

Parallel Lines m1 = m2

Perpendicular lines m1 = -1 / m2

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Point-Slope Form of a Line Slope-Intercept Form y = mx + b

Given an equation, it’s easy to find its slope and y-intercept, and graph it Standard Form Ax + By = C

Given an equation, it’s easy to find both intercepts, using them to graph it Point-Slope Form (y – y1) = m(x – x1)

Given a slope and any point, it’s easy to write a line’s equation

2.5 3

Writing a Line’s Graph using the slope and any one point (x1,y1)

Was this stepReally Necessary?

(3,4)(5,3)

2.5 4

Writing an Equation in Function Form (slope/intercept):What if all we know are 2 points on a line?

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Application

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Slopes of Parallel Lines m1 = m2

But wait! How can you be sure that it’s not the same line ?

AND differenty-intercepts!

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Slopes of Perpendicular Lines m1 = -1 / m2

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Slopes of Perpendicular Lines m1 = -1 / m2

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Overview - 2.6 The Algebra of Functions