From an analytical point of view, a quadratic equation has no (real) solution if the discriminant is negative.
In fact, the equation for the solution involves the quantity
, where a,b and c are the coefficient of the equation
.
Since we can't compute the square roots of negative numbers using real numbers, if
the equation has no solution.
From a geometric point of view, the solutions of an equation are the points where the graph of the equation intersects the x axis. So, if a parabola (i.e. the graph of a quadratic polynomial) has no solutions, it means that its graph never intersercts the x axis.