What number must i add to complete the square x^2+8x=-3

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

What is 1/3x5 on anuber line what does it look like on a number line

Onnie is considering doing some long term investing with money that she inherited. she would like to have $50,000 at the end of 30 years. approximately how much money would lonnie need to put into an account earning 6% interest compounded annually in order to meet her goal?