How do I know when to use the -B formula?
Hey the hint is normally in the question like *to two decimal places*
if when u try to do a regular quadratic and its un solvable:)
You can actually use it as your default method, if you prefer not to get into factorising the quadratic.
It works even when the roots are whole numbers, so it's actually a more general method of solving a quadratic than the factorising method, which only works for rational roots.
Give it a go and see for yourself :-)