Question

What are the solutions to the equation y2 – 1 = 80?

–5 and 5

–4 and 4

–7 and 7

–9 and 9

Answer 1

for this question you should first add +1 on both sides of the equation so you will have:
y^2 = 80 + 1 
y^2 = 81 
so the square root of 81 is 9 and -9 so y equals to 9 and -9 :)))
i hope this is helpful
have a nice day

Answer 2

$y^2 - 1 = 80\\\\y ^2 = 81\\\\y =\sqrt{81}\\\\ y = \pm 9\\\\ y=9\\y = -9$

Your final answer is -9 and 9.