direct variation y = mx (no b) lines that go through the origin y intercept of zero slope also...
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Direct Variation
• y = mx (no b)
• Lines that go through the origin
• Y intercept of zero
• Slope also called constant of variation (variation constant)
Examples of Direct Variationy = -2x y = 2x
Checking for Direct Variation
Graph --> is it a straight line through the origin?
Equation --> does it fit y = mx?(may need to solve for y)
Do these lines illustrate direct variation?
y = -1/2x x = -3
What is the variation constant?y = -1/2x x = -3
Are these equations direct variation?
y = 5x
y = -3/4x
y = -2x - 7
Are these equations direct variation?
y = 5x --> Yes!
y = -3/4x --> Yes!
y = -2x - 7 --> No (y-int not 0)
Are these equations direct variation?
2x + y = 0
-x + y = -1
4x - 5y = 0
Are these equations direct variation?
2x + y = 0 --> y = -2x --> YES
-x + y = -1 --> y = x - 1 --> NO
4x - 5y = 0 --> y = 4/5x --> YES
Online Animation
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Homework
p256 #2-8 E,
11-22 C6,
58-62 E