section 4.5 direct variation. what happens to y as x goes up by 1?
TRANSCRIPT
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Section 4.5
Direct Variation
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What happens to Y as X goes up by 1?
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What happens to Y as X goes up by 1?
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Direct Variation
Two variables x and y vary directly if
y = kx
K is a constant number that is not zero. K could be positive or negative.
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Direct VariationTwo variables x and y vary directly if
y = kx
Basically, x and y are changing at a constant rate.
As x goes up, y also goes up at a rate of k.
OrAs x goes up, y is going down at a rate of k.
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Writing a direct variation equationThe variables x and y varies directly;
When x=5, y=20.
• Y=KX write model for direct variation
• 20=K(5) substitute 5 for x and 20 for y.
• /5 /5 divide each side by 5
• 4=K• So, the equation is y = 4x
• Find the value of y when x=10.• y=4(10) substitute 10 for x and y=4
• Y=40
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The variables x and y vary directly. When x=4,y=6 A) write an equation that relates x and yB) find the value of y when x=12.
• SOLUTION• A. Because x and y vary directly, the equation is of the form • y= kx. You can solve for k as follows.• Y= kx write model for direct variation.
• 6= k(4) substitute 4 for x and 6 for y
• 1.5= k divide each side by 4
• Therefore, the equation is y = 1.5 x or y = 3/2 x
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Direct variation equation
• An equation that relates X is Y=1.5x
• B) y=1.5(12) substitute 12 for x in y=1.5x Y=18 simplify when X=12, y= 18
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The variables x and y vary directly. When x=8,y=3 A) write an equation that relates x and yB) find the value of y when x=12.
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Homework
Text Page 238, # 23-31 All
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