How to do it on calculator

The best way to do math on a calculator is to turn it over and use it as a backboard for your writing. :)

I thin you need to check what you wrote. Is it or is it ? If it's the second one use the identity and the solution falls out of the bottom. If it's the first one, that can be rough, when I solved it I needed the quadratic formula and the identity , so I can can see your difficulty. If it's the first one, give me an honest effort and show me what you've done and I'll show you how to do it.