Question

Determine the solution set of x^2 - 80 = 0.

a) {±2}
b) {±}
c) {±4}

Answer 1

so add the 80 over and take the square root, right? The square root of 81 is +/- 9, so you're answer should be close to that. Is that all it gives for b?

Answer 2

no sorry I posted the options wrong.
a) {±2 square root of 5}
b) {± square root of 5}
c) {±4 square root of 5}
@caseyrt

Answer 3

ah ok. So you've taken the square root of 80, right? But you can divide 80 by a perfect square. Try dividing it by 4, 9 and 16 and see what you get. Then you can factor out that perfect square to the outside and leave the rest inside the root.

Answer 4

\[\sqrt{80} = \sqrt{16*5} = +/- 4 \sqrt{5}\]