**Please help me. I need to explain the answer in full detail but I don't understand how. Sorry...**

Guest Aug 23, 2018

#1**+1 **

If the quadratic function opens downward, we will have a negative sign in front of the x^2 term...so we can eliminate the last two answers right away

In the form ax^2 + bx + c, the x coordinate of the vertex = -b / [ 2a]

Look at answer B.....letting a = -1 and b = 4....the x coordinate of the vertex is

-4 / [ 2 * -1 ] = -4 / -2 = 2

To find the y value associated with this x value, put this "2" back into the function

-(2)^2 + 4(2) + 1 =

-4 + 8 + 1 =

-4 + 9 =

5

So....this function turns downward and has a vertex of (2, 5)

Here's a graph to confirm this : https://www.desmos.com/calculator/tlavaymezd

CPhill Aug 23, 2018