The original problem was this: Find the smallest possible value of $ax^2+bx+c$, where a, b, and c are given numbers and $a>0$, and x is some number.
I already asked this, and got a decent answer, but let me get this clear; am I correct here?
The smallest possible value of $ax^2+bx+c=a(-b/2a)+b(-b/2a)+c$. You get it by plugging $-b/2a$ into the place of $x$. Would you call it a decent answer? Any suggestions to improve it?
If you know why you have replaced x by -b/2a to get the minimum value then surely that is a decent answer.