Some quadratics cannot be factorised. An alternative method to solve a quadratic equation is to complete the square. To solve an equation of the form \(x^2 + bx + c = 0\) consider the expression ...

c\). To get \(b\) (the number inside the bracket), halve the coefficient (number in front) of the second term in the original equation. Half of -6 is -3 so the bracket becomes \((x-3)\).