SOLUTION: I need help solving this equation: {{{9a=-a^2-18}}}

Question 227736: I need help solving this equation:
Found 2 solutions by jim_thompson5910, drj:
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
Start with the given equation.

Subtract 9a from both sides.

Notice that the quadratic is in the form of where , , and

Let's use the quadratic formula to solve for "a":

Start with the quadratic formula

Plug in , , and

Negate to get .

Square to get .

Multiply to get

Subtract from to get

Multiply and to get .

Take the square root of to get .

or Break up the expression.

or Combine like terms.

or Simplify.

So the solutions are or
Answer by drj(1380) (Show Source): You can put this solution on YOUR website!
I need help solving this equation:

Step 1. Add to both sides of the equation.

where we simplified and arranged in descending order.

Step 2. To solve, use the quadratic equation given as

where a=1, b=9 and c=18.

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=9 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: -3, -6. Here's your graph:

Step 3. ANSWER: The solutions are -3 and -6.

I hope the above steps were helpful.

For FREE Step-By-Step videos in Introduction to Algebra, please visit http://www.FreedomUniversity.TV/courses/IntroAlgebra and for Trigonometry visit http://www.FreedomUniversity.TV/courses/Trigonometry.

And good luck in your studies!

Respectfully,
Dr J
http://www.FreedomUniversity.TV

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