$$0 = a(x^2 + \frac ba x) + c = a(x^2 + \frac ba x + \frac{b^2}{4a^2}) -\frac{b^2}{4a} + c$$
$$= a(x + \frac b{2a})^2 + c - \frac{b^2}{4a}$$
It is more than obvious that the above equation simplifies to the Quadratic Formula, yet I was curious as to why the method of simplifying is done as seen above from the original
$ax^2 + bx + c = 0$ in that way, for instance how does it become $a(x^2 + \frac bax) + c$?
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Divide the first two terms by $a$. – Pakquebchsoflwty Oct 26 '14 at 15:39
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"for instance how does it become a(x^2+(b/a)x)+c?" – Pakquebchsoflwty Oct 26 '14 at 15:42
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1There was an MSE discussion of the quadratic formula quite a hile ago that may be interesting to you. – André Nicolas Oct 26 '14 at 15:44