Question 125323
To find the axis of symmetry, use this formula:


{{{x=-b/(2a)}}}


From the equation {{{y=-2x^2-20x-47}}} we can see that a=-2 and b=-20


{{{x=(--20)/(2*-2)}}} Plug in b=-20 and a=-2



{{{x=20/(2*-2)}}} Negate -20 to get 20



{{{x=(20)/-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.