U N I T 5 S E C T 4 W R I T I N G A F U N C T I O N R U L E
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Transcript of U N I T 5 S E C T 4 W R I T I N G A F U N C T I O N R U L E
WRITING
A
FUNCTION
RULE
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13
02
-11
f(X)XStart out by asking yourself, “How do I get from 1 to -1?”
How do I get from 2 to 0?
How do I get from 3 to 1?
How do I get from 4 to 2?
f(x) = X – 2
-2
-2
-2
-2
84
63
42
21
YX Ask yourself, “How can I get from 1 to 2?
How can I get from 2 to 4?
How can I get from 3 to 6?
How can I get from 4 to 8?
Which one makes the rule?
Y = 2X
+1 or 2(1)
+2 or 2(2)
+3 or 2(3)
+4 or 2(4)
97
86
75
64
53
42
31
YXHow do I get from 1 to 3?
How do I get from 2 to 4?
How do I get from 3 to 5?
How do I get from 4 to 6?
Y = X + 2
+2
+2
+2
+2
63
41
2-1
0-3
f(x)X How do you get from -3 to 0?
How do you get from -1 to 2?
How do you get from 1 to 4?
How do you get from 3 to 6?
f(x) = x + 3
+3
+3
+3
+3
00
-1-2
-2-4
-3-6
-4-8
f(x)X How do you get from -8 to -4?
How do you get from -6 to -3?
How do you get from -4 to -2?
How do you get from -2 to -1?
Which one makes the rule?
f(x) = x/2
Does this hold true for 0?
/2 or +4
/2 or + 3
/2 or +2
/2 or +1
REAL WORLD PROBLEM SOLVING
A carpenter buys finishing nails by the pound. Each pound of nails costs $1.l9. Write a function rule to describe this relationship.
Let x = the number of pounds of nails
Let C(x) = the cost of x pounds of nails
4.764
3.573
2.382
1.191
C(x)X C(x) = 1.19x
How much would 12 lb of finishing nails cost?
C(12) = 1.19(12)
C(12) = 14.28
Suppose you buy a word-processing software package for $199. You charge $15 per hour for word processing. Write a rule to describe your profit as a function of the number of hours you work.
Let n = number of hours you work
Let p(n) = the profit you will make
Think:
Total is $15 times hours minus cost of
Profit worked program
P(n) = 15n – 199
THE END
