How to prove that i don't need to find a discriminant to solve the quadratic y^2+6y+9=0?

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The solutions of the quadratic equation y^2 + 6y + 9 = 0 can easily be found without finding the discriminant.

y^2 + 6y + 9 = 0

=> y^2 + 3y + 3y + 9 = 0

=> y( y + 3) + 3(y + 3) = 0

=> (y + 3)^2 = 0

=> y = -3

Or you can use the formula (a + b)^2 = a^2 + b^2 + 2ab.

The solution of the quadratic equation obtained without finding the discriminant is -3

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