Lesson Graphing Equations in Standard Form by Two-Intercept Method

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This Lesson (Graphing Equations in Standard Form by Two-Intercept Method) was created by by rapaljer(2773) About Me : View Source, Show
About rapaljer: Retired Professor of Mathematics from Seminole Community College after 36 years.

GRAPHING EQUATIONS in STANDARD FORM by the TWO-INTERCEPT METHOD

When the equation of a line is given in STANDARD FORM, so the easiest way to graph it is probably the TWO-INTERCEPT METHOD. Instead of having to solve for y in terms of x in order to find the slope and y-intercept, I think it is much easier to just find the x and y intercepts.

EXAMPLE 1: 2x+y = -2
SOLUTION:
2x+y = -2
If x= 0, then y = -2
If y=0, then 2x= -2, so x= -1
Graph these points and connect the dots. It should look like this:
graph(300,300, -6,6,-6,6, -2x-2)
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EXAMPLE 2: 3x-6y=-3
SOLUTION:
3x - 6y = -3
If x = 0, then -6y=-3, so y= 1/2
If y=0, then 3x = -3, so x = -1
Graph these points and connect the dots. It should look like this:
graph(300,300, -6,6,-6,6, (1/2)*x+(1/2))
----------------------------------------------------------------------------------

EXAMPLE 3: -2x+y=-2
SOLUTION:
-2x + y = -2
If x = 0, then y=-2
If y=0, then -2x = -2, so x = 1
Graph these points and connect the dots. It should look like this:
graph(300,300, -6,6,-6,6, 2x-2)
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EXAMPLE 4: (1/4)*x+(3/4)*y=6
SOLUTION:
(1/4)*x+(3/4)*y=6

First multiply both sides by the LCD which is 4:
4*(1/4)x+4*(3/4)y=4*6
x + 3y = 24

If x = 0, then 3y=24, so y= 8
If y=0, then x = 24 (This will take a LARGE GRAPH!)
Graph these points and connect the dots. It should look like this:
graph(300,300, -10,30,-10,30, (-1/3)*x+8 )

R^2 at SCC

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