(iii)
(y – 2) (y + 2) = 0
Sol.
(y
– 2) (y + 2) = 0
∴ (y)2 – (2)2 = 0
[∵ a2 – b2 = (a + b) (a
– b)]
∴ y2 – 4 = 0
∴ y2 + 0y – 4 = 0
Here a = 1, b = 0, c = – 4
are real numbers
where a ≠ 0
So it is a quadratic
equation in variable y.