FRIDAY

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FRIDAY

• You will need a CALCULATOR today.
• Use your own or check one out with your ID or
  cell phone

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Warm-up

• Given this 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 this 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
• Monday is Quiz 2
• Wednesday is your first UNIT TEST (60)

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Quiz Corrections

• Correct any problems you missed (except bonus)
• Due on test day!!
• Show all work for the reworked problems. Dont
  just give a new answer!
• Graded for accuracy based on
• How many were wrong
• How many did you fix
• How many were correct

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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 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 Drug
Manufacturing
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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 3 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 Water Depth
versus Time of dive
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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 1-6 (answers on website)
• Quiz next class