When solving a quadratic equation, such as this, we need to factorize first:

x^2+6x+8 = 0

=> (x+4)(x+2) = 0

So x = -4 or x = -2

Why can't we do x(x+6) = -8?

And so x = -8 or x = -6 (obviously wrong)

Shucks, learnt this in sec sch but cant remeber the reason... only know it's illegal unless the RHS is a zero to begin with...

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