WAEC 2022 · Paper 1 · Q1

Binary operations

A binary operation $\Delta$ is defined on the set of real numbers, $R$ , by $x \Delta y = \sqrt{x + y - \dfrac{xy}{4}}$ , where $x, y \in R$ . Find the value of $4 \Delta 3$ .

Worked solution (try it first)

Put $x = 4$ and $y = 3$ into the rule: $4 \Delta 3 = \sqrt{4 + 3 - \dfrac{4 \times 3}{4}}$ .
Inside the root, $\dfrac{12}{4} = 3$ , so you have $4 + 3 - 3 = 4$ .
The square root of 4 is 2, so $4 \Delta 3 = 2$ , option D.

Report a problem with this question