Having trouble with a discriminant equation

[alexcampbeel]

Hi there, not sure if I'm posting in the right section, very new to this.

I have a question in my revision sheets which I am stumped by:

'A parabola has equation y=ax²+bx+c, where a is positive. Show the that the minimum y value is given by the expression = -∆/4a, where ∆=b²-4ac.'

I have tried and tried but I don't know where to go with this, any help would be greatly appreciated.

 

[Ishuda]

Hi there, not sure if I'm posting in the right section, very new to this.

I have a question in my revision sheets which I am stumped by:

'A parabola has equation y=ax²+bx+c, where a is positive. Show the that the minimum y value is given by the expression = -∆/4a, where ∆=b²-4ac.'

I have tried and tried but I don't know where to go with this, any help would be greatly appreciated.

What is the value of x at the minimum? Plug that into the equation for the parabola and see what you get.

 

[stapel]

I have a question in my revision sheets which I am stumped by:

Since it's on your review sheet, then you must have seen the required material before. So:

'A parabola has equation y=ax²+bx+c, where a is positive. Show the that the minimum y value is given by the expression = -∆/4a, where ∆=b²-4ac.'

What have you learned about max/min points of parabolas, as relates to their vertices? What have you learned about vertices, as relates to completing the square of the original quadratic function?