NECO 2023 · Paper 1 · Q19

Variation

$y$ is partly constant and partly varies as $x$ . When $y = 2$ , $x = 3$ and when $y = 5$ , $x = 6$ . Find the relationship between $x$ and $y$ .

Worked solution (try it first)

Partly constant and partly varies as $x$ : $y = a + bx$ .
$a + 3b = 2$ and $a + 6b = 5$ .
Subtract: $3b = 3$ , so $b = 1$ .
Then $a = 2 - 3 = -1$ , so $y = x - 1$ , option B.

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