Find the rule of the mapping: 1\;\;\;2\;\;\;3\;\;\;\;4\;\;\;\;5\;. . .\;x \;\;\;\;\;\;\;\;\;\;\;\; 7\;\;11\;\;15\;\;19\;\;23\;. . . .\;y

Correct Answer is : x⟶4x+3x 4 x + 3x⟶4x+3

Correct Answer is : x⟶4x+3x 4 x + 3x⟶4x+3

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BECE Mathematics 2010 Paper

Question : 24

Total: 40

1\;\;\;2\;\;\;3\;\;\;\;4\;\;\;\;5\;. . .\;x

\downarrow\;\;\downarrow\;\downarrow\;\downarrow\;\;\downarrow\;\;\;\;\;\;\downarrow

7\;\;11\;\;15\;\;19\;\;23\;. . . .\;y

Solution:

Concept:

The

y

values increase by a fixed number while

x

increases by

1

, so the rule is a linear expression in

x

Explanation:

From the mapping:

x = 1, 2, 3, 4, 5

gives

y = 7, 11, 15, 19, 23

The constant difference between consecutive

y

values is

4

Since

y

increases by

4

for each increase of

1

x

, the rule must be of the form

y = 4x + c

Use the first pair

x = 1

y = 7

7 = 4(1) + c

c = 3

Therefore, the rule is

y = 4x + 3

Answer:

C.\;\; x \longrightarrow 4x + 3

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