SOLUTION: What is the equation of the axis of symmetry of the function y=-2x^2-20x-47? I think the answer is x=-5 but I'm not sure. Can someone please explain?

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: What is the equation of the axis of symmetry of the function y=-2x^2-20x-47? I think the answer is x=-5 but I'm not sure. Can someone please explain?      Log On


   

Question 125323: What is the equation of the axis of symmetry of the function y=-2x^2-20x-47? I think the answer is x=-5 but I'm not sure. Can someone please explain?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
To find the axis of symmetry, use this formula:

x=-b%2F%282a%29

From the equation y=-2x%5E2-20x-47 we can see that a=-2 and b=-20

x=%28--20%29%2F%282%2A-2%29 Plug in b=-20 and a=-2


x=20%2F%282%2A-2%29 Negate -20 to get 20


x=%2820%29%2F-4 Multiply 2 and -2 to get -4



x=-5 Reduce


So the axis of symmetry is x=-5 which means that you are correct.