SOLUTION: Hi, I'm doing exam review and a crucial section I need to know I cannot remember. This question I'm unsure of how to attempt. Thanks to the person that solves it. Using the meth

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons -> SOLUTION: Hi, I'm doing exam review and a crucial section I need to know I cannot remember. This question I'm unsure of how to attempt. Thanks to the person that solves it. Using the meth      Log On


   

Question 975640: Hi, I'm doing exam review and a crucial section I need to know I cannot remember. This question I'm unsure of how to attempt. Thanks to the person that solves it.
Using the method indicated, determine the minimum or maximum value of each of the following and state the X value for which it occurs.
A) y=x^2+8x-5 by partial factoring
B) y=-3x^2-12x+7 by completing the square
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
(A), partial factoring for max or min of y=x^2+8x-5, but what kind of method is "partial factoring"? I never heard of that. The quadratic polynomial you have on the right hand side is not factorable.

I would just use general solution to get the zeros, and find the x value in the middle.

Zeros: %28-8%2B-+sqrt%2864%2B4%2A5%29%29%2F2

%28-8%2B-+sqrt%2812%2A7%29%29%2F2

%28-8%2B-+2%2Asqrt%2821%29%29%2F2

highlight_green%28-4%2B-+sqrt%2821%29%29, the zeros for the equation

Find Middle x value of the zeros:
Just same as finding the average of the zeros,
%28-4%2Bsqrt%2821%29%2B%28-4%29-sqrt%2821%29%29%2F2
%28-8%2B0%29%2F2
highlight%28-4%29
-
The corresponding y value:
y=%28-4%29%5E2%2B8%2A%28-4%29-5
16-32-5
-16-5
highlight%28-21%29, a minimum value.


(B):
Study the lessons on Completing The Square.
How to Complete The Square is included in this how-to-solve quadratic equation lesson.
Visually showing what Completing The Square means