Question 1151571

Find the maximum/minimum value and the value of x when it occurs by completing the square.

a) y=5x^2-40x+81

b) y=-3x^2-30x-79
<pre>When you have completed the square on a), you should get the VERTEX form of a quadratic equation: {{{matrix(1,3, y, "=", 5(x - 4)^2 + 1)}}}, which you now need to compare to the 
equation: {{{matrix(1,3, y, "=", a(x - h)^2 + k)}}}, with (h, k) or in this case, (4, 1) being the vertex. 
And, with the given equation having an "a" value that's > 0, this parabola will have a {{{highlight_green(matrix(1,6, MINIMUM, VALUE, of, y, "=", 1))}}}, since k = 1. 
You should now be able to follow this concept and answer b)!