Geometry 3.5Geometry 3.5

Big Idea: Write Big Idea: Write and Graph and Graph

Equations of Equations of LinesLines

Reminder: One Way to Write a Reminder: One Way to Write a Linear Equation is Linear Equation is

Slope-Intercept FormSlope-Intercept Form

y = mx + by = mx + b

m = slope m = slope

b= y-interceptb= y-intercept

y-intercepty-intercept: point where : point where line crosses (intercepts) line crosses (intercepts) the the

y-axis (x = 0)y-axis (x = 0)

x-interceptx-intercept: point where : point where line crosses the x-axis line crosses the x-axis (y=0)(y=0)

Example: Write the equation of the given line.

Example: Given a line passes through the points (5,3) and (2, -6), write the equation of the line.

Ex.1) Find the equation of the line ║ to the line y = 5x – 2 that passes through the point (-3, 1).

Ex.2) Find the equation of the line ┴ to the line y = 5x – 2 that passes through the same point (-3, 1).

Standard FormStandard Form: Another : Another way to write a linear way to write a linear equation:equation:

ax + by = cax + by = c

(a, b and c represent (a, b and c represent numbers)numbers)

Ex.) Rewrite the equation in standard form.

Ex: Write the equation in standard form.

Ex: Graph the equation.

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 1 2 3 4 5 6 7 8 9 10x

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Ex: Graph the equation.

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 1 2 3 4 5 6 7 8 9 10x

-10

-9

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Remember, Remember,

If If no no ‘‘xx ’’ in equation, it in equation, it’’s a s a horizontalhorizontal line.line.

If If no no ‘‘yy ’’ in equation, it in equation, it’’s a s a verticalvertical line.line.