The second method of solving quadratics is square root property,

                                                 If p²  = d          then       p =±d

There is a (potentially) new symbol that we have to define first in case you haven't seen it still.  The symbol "± " is named as : "plus or minus" & i.e. exactly what this tells us. This symbol is shorthand which tells us that we actually have two numbers here.  One is  p =√d  and the other is p = √- d . 

It is a fairly simple property to use, however it can just used on a small portion of the equations which we're ever likely to encounter.  Let's see some examples of this property.