This is a basic question but I can seem to explain it. The Quadratic Equation term "b^2 -4ab" why do we change it to "b^2+ 4ab" when the "b" value is negative? Thanks annmrj@aol.com

EX: b^2-4ab (x^2-6x-27=0) = 6^2+4(1)(-27)=144