x²+6x-2 = 0

We use completing the square when the equation cannot be factorised. Begin by placing x²in 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)

Factorise X^2-X-20

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