The mapping below relates x to y. x 1 2 3 4 y 2 5 10 17 What is the rule for the mapping?

Correct Answer is : x→x2+1x → x² + 1x→x2+1

Correct Answer is : x→x2+1x → x² + 1x→x2+1

BECE Mathematics 2020 Paper

Question : 26

Total: 40

x

y

$x$	$1$	$2$	$3$	$4$
$y$	$2$	$5$	$10$	$17$

Solution:

Concept:

The rule of a mapping must give the correct output

y

for every input

x

. Test each option with the given pairs.

Solution:

Pairs:

1 \to 2

2 \to 5

3 \to 10

4 \to 17

All four rules give

2

when

x = 1

, so check

x = 2

3(2)^2 - 1 = 11 \ne 5

5(2)^2 - 3 = 17 \ne 5

(2)^2 + 1 = 5

✓

4(2) - 2 = 6 \ne 5

Check C with the other pairs:

3^2 + 1 = 10

✓ and

4^2 + 1 = 17

✓.

Key point: One pair is not enough: every option fits

1 \to 2

. Test a second pair before choosing.

Answer:

Option C (

x \to x^2 + 1

)

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