Question

What are the solutions to the equation y2 – 1 = 15?

–5 and 5

–4 and 4

–7 and 7

–9 and 9

Answer 1

-4 and 4. Those are the answers.

Answer 2

The solution of y² - 1 = 15 is +4 and -4

Explanation:

Given

y² - 1 = 15

Our solution goes thus;

Make y² the subject of formula

y² = 15 + 1

Add 15 to 1

y² = 16

Take square roots of both sides

√y² = √16

y = √16

Note that the square root of 16 is either +4 or -4 because +4 * +4 = 16 and -4 * -4 = 16; So, we replace √16 with ±4 which means + or -4

y = ±4

y = +4 and -4

Hence, the solution of y² - 1 = 15 is +4 and -4