-b/2a came from the fact that this is a quadratic equation which means if you differentiate it you'll get 4x+5, and minimum or maximum occurs where dy/dx = 0, so 4x + 5 = 0, so x = -1.25 . Plug in this in the equation to get 0.875. We know that equation is opening upward (positive coefficient of x^2) and therefore 0.875 is the minimum.
thanks a bunch I've got an upcoming SAT test and I'm doing really good but then stumbled on a question in which I must calculate the minimum value of the function. I read its explanation but was left puzzled as it used a rule of: a(x-h)+k where h is the minimum I have not yet taken this specific rule at school so yours is a life saver
Hey there! There is also this formula they taught us at 10th grade. to find the maximum or minimum value without finding the x in : ax² + bx + c you can simply devide Δ by 4a to find the value of Y.
Can someone please explain how he got f(-1.25)=0.875 at the end? I don't know how he solved f(-125)=2(-125)2+5(-125)+4 to get 0.875 I'm super confused.