SOLUTION: Hi. I really need help with an equation that needs to be graphed, also I need to find the coordinates of the vertex. The equation is y= -x^2 - 8x - 7

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: Hi. I really need help with an equation that needs to be graphed, also I need to find the coordinates of the vertex. The equation is y= -x^2 - 8x - 7      Log On


   

Question 204134This question is from textbook
: Hi. I really need help with an equation that needs to be graphed, also I need to find the coordinates of the vertex. The equation is y= -x^2 - 8x - 7 This question is from textbook

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
i. I really need help with an equation that needs to be graphed,
also I need to find the coordinates of the vertex.
The equation is y= -x^2 - 8x - 7
:
Plot the graph from x=-8 to x= 0; should look like this:
+graph%28+300%2C+200%2C+-10%2C+4%2C+-10%2C+12%2C+-x%5E2-8x-7%29+
:
Find the vertex by finding the axis of symmetry; x = -b/(2a)
in the equation a=-1, b=-8
x = %28-%28-8%29%29%2F%282%2A-1%29
:
x = 8%2F%28-2%29
:
x = -4 is the x coordinate of the vertex
:
Find y, substitute -4 for x in the equation
y = -(-4^2) - 8(-4) - 7
y = -16 + 32 - 7
y = +9
;
Vertex: -4,+9 as shown on the graph