9.1 Inverse

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9.1 Inverse Joint Variation
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Objectives/Assignment
Write and use inverse variation models Write and
us joint variation models Assignment 21-47 odd
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Just a reminder from chapter 2

• Direct Variation
• Use ykx.
• Means y varies directly with x.
• k is called the constant of variation.

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New stuff!

• Inverse Variation
• y varies inversely with x.
• k is the constant of variation.

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Ex tell whether x y show direct variation,
inverse variation, or neither.

1. xy4.8
2. yx4

Inverse Variation
Hint Solve the equation for y and take notice
of the relationship.
Neither
Direct Variation
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Ex The variables x y vary inversely, and y8
when x3.

• Write an equation that relates x y.
• k24
• Find y when x -4.
• y -6

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Joint Variation

• When a quantity varies directly as the product of
  2 or more other quantities.
• For example if z varies jointly with x y,
  then zkxy.
• Ex if y varies inversely with the square of x,
  then yk/x2.
• Ex if z varies directly with y and inversely
  with x, then zky/x.

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Examples Write an equation.

• y varies directly with x and inversely with z2.
• y varies inversely with x3.
• y varies directly with x2 and inversely with z.
• z varies jointly with x2 and y.
• y varies inversely with x and z.