Why do I get a weird answer when calculating this?

Because "a +bi" is a Complex mode. And you will get "weird" answers. If you haven't taken "complex Math", then you wouldn't understand it. If that is the case, ignore your friend's suggestion and use your calculator in "normal" mode.

((-1*0.056)-√(0.056²-(4*1*0.056)))/2)

((-0.056)-√(0.003136-0.224))/2)

(0.003136-0.224) is less than 1 and there are no real solutions to the square root of a negative number.

so

This has no real solutions

It has complex solutions but they are imaginary numbers so you don't need to worry about those. :)

paste ((-1*0.056)-√(0.056²-(4*1*0.056)))/2 in WEB 2.0 CALC

replace √ by sqrt (same meaning)

replace 0.056² by 0.056^2 (same meaning)

hit =

and you'll get your answer:  -((7/250))-0.2349808502837076i