SOLUTION: how to find the equation of line of symmetry for y=9-8x-x^2 i have tried by using the completiing the square method and got the answer in surd form. my answer is 4 root 7.

Question 204373: how to find the equation of line of symmetry for y=9-8x-x^2
i have tried by using the completiing the square method and got the answer in surd form. my answer is 4 root 7.
Answer by ichudov(507) (Show Source): You can put this solution on YOUR website!
Try graphing it:

That would give you some idea.
Then you can solve quadratic equation and note that the line of symmetry is between roots::

Solved by pluggable solver: SOLVE quadratic equation with variable

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=100 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: -9, 1. Here's your graph:

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