FRIDAY

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FRIDAY

• You need a CALCULATOR
• Use your own or check one out with your ID or
  cell phone
• Pickup WS 1-3

2
Warm-up

• Given relation (2, -3), (4, 1), (-5, -3), (-1,
  1)
• Domain
• Range
• Is it a function? Yes/ No
• Are these 2 graphs functions?

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Warm-up

• Given relation (2, -3), (4, 1), (-5, -3), (-1,
  1)
• Domain -5, -1, 2, 4
• Range -3, 1
• Is it a function? Yes/ No

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Announcements

• TODAY ends the 2nd week of this 5 week grading
  period
• TODAY is the last day to makeup Unit 1 Quiz 1
• Mini Quiz Tuesday

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Sections 2-5 8-1

• Direct Inverse Variations

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Objectives

• I can recognize and solve direct and inverse
  variation word problems.
• I can determine which graph models each type of
  variation

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Direct Variation
As one variable increases, the other must also
increase ( up, up) OR As one variable decreases,
the other variable must also decrease. (down,
down)
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Real life?

• With a shoulder partner take a few minutes to
  brainstorm real life examples of direct
  variation. Write them down.

Food intake/weight Exercise/weight loss Study
time/ grades Hourly rate/paycheck size Stress
level/blood pressure Recipes Paint Mixtures
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Direct Variation

• y kx
• k is the constant of variation
• the graph must go through the origin (0,0) and
  must be linear!!

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Direct Variation
Ex 1)If y varies directly as x and y 12
when x 3, find y when x 10.
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Solving Method
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Direct Variation Application

• Ex In scuba diving the time (t) it takes a
  diver to ascend safely to the surface varies
  directly with the depth (d) of the dive. It
  takes a minimum of 3 minutes from a safe ascent
  from 12 feet. Write an equation that relates
  depth (d) and time (t). Then determine the
  minimum time for a safe ascent from 1000 feet?

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Your TURN 1 on Homework

• Find y when x 6, if y varies directly as x and
  y 8 when x 2.

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Inverse Variation
As one variable increases, the other decreases.
(or vice versa)
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Inverse Variation

• This is a
• NON-LINEAR function (it doesnt look like
  ymxb)
• It doesnt even get close to (0, 0)
• k is still the constant of variation

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Real life?

• With a shoulder partner take a few minutes to
  brainstorm real life examples of inverse
  variation. Write them down.

Driving speed and time Driving speed and gallons
of gas in tank Pressure versus Volume
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Inverse Variation
Ex 3) Find y when x 15, if y varies inversely
as x and when y 12, x 10.
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Solving Method
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Inverse Variation Application
ExThe intensity of a light I received from a
source varies inversely with the distance d
from the source. If the light intensity is 10
ft-candles at 21 feet, what is the light
intensity at 12 feet? Write your equation first.
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Your TURN 7 on Homework
Find x when y 5, if y varies inversely as x and
x 6 when y -18.
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Direct vs. Inverse Variation
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Homework

• WS 1-3 (answers on website)
• Mini Quiz next class