What is meant by repeated root?

What will be the repeated root of an equation like

ax^2 + bx + c = 0

repeated roots means equal or same roots of a quadratic.thus the graph touches x axis only at one point.for the equation

ax^2 + bx + c = 0 is (-b/2a) but only when b²-4ac=0

repeated roots iz tht ur eqn iz a perfect square....nd willl touch d x axis only 1ce....

fr ur eqn b²=4ac!!!! so tht d discriminant bcums zero!!!!
nd u get ur repeated root ie "-b/2a "