Show that the roots of $ax^2+(a+b)x+b=0$ are real for all values of a and b.
I know that for the roots of the equation to be real the discriminant must be greater than zero.
So I've done $b^2-4ac=(a+b)^2-4ab $ and then expanded to $a^2+b^2-2ab$. But I don't see how this gives me a positive discriminant.
This is where I'm stumped, and don't know how to progress.
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