you are correct so far.
Note that the discriminant is 144-72 = 72, which is not a perfect square. So, the roots will not be rational, and the quadratic formula is your best bet.
Or, you can complete the square.
5(x^2+12x+18) = 0
x^2+12x+18 = 0
x^2+12x+36 = 18
(x+6)^2 = 18
x+6 = ±√18
x = -6±√18 = -6±3√2
Factor: 5(x+6)^2-90
I am able to simplify this expression to 5(x^2+12x+18), but i'm stuck on trying to solve the rest of this. I understand that you can use the quadratic formula, but I want to refrain from doing so as this question should be utilising perfect squares/difference of two squares.
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