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BECE Mathematics 2021 Paper

Question : 16

Total: 40

Find

x

y=37

Solution:

Concept:

The mapping follows a linear pattern, so use the formula for the

n^{\text{th}}

term of an arithmetic sequence to find the relation between

x

and

y

Explanation:

From the mapping, consecutive

y

-values increase by a common difference.

9 - 5 = 4

13 - 9 = 4

17 - 13 = 4

21 - 17 = 4

Therefore, the relation is linear.

For an arithmetic sequence,

U_n = U_1 + (n-1)d

Here,

U_1 = 5

d = 4

, and

n = x

So,

y = 5 + (x-1)4

y = 5 + 4x - 4

y = 4x + 1

Now substitute

y = 37

37 = 4x + 1

37 - 1 = 4x

36 = 4x

x = \frac{36}{4} = 9

Answer:

x = 9

, which is option D.

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