How do you complete the square to answer quadratic equations?
x2+6x-2 = 0
We use completing the square when the equation cannot be factorised. Begin by placing x2 in the brackets and halving the number in front of the x (also known as the coefficient of x) to form (x+3)2 . Now if we expanded the brackets and we would have x2 +6x+9. Since +9 is not part of the original equation we must subtract it giving (x+3) 2 -9. Returning to the original equation we must also -2 giving us (x+3)2-11.
x2+6x-2 = (x+3)2 -11 = 0 so to solve, we treat like a normal equation.
(x+3)2 = 11
(x+3) = √(11)
x=-3+/-√(11)
MM
