SOLUTION: Solve the equation 5(x2−20) = 2x(3+x)−40, giving your answers to 5 decimal places

Algebra.Com
Question 1005954: Solve the equation 5(x2−20) = 2x(3+x)−40,
giving your answers to 5 decimal places
Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
Use ^ (Shift 6) for exponents.
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Solve the equation 5(x^2 - 20) = 2x(3+x) - 40
5x^2 - 100 = 6x + 2x^2 - 40
3x^2 = 6x + 60
x^2 - 2x - 20 = 0
Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)
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=84 is greater than zero. That means that there are two solutions: .




Quadratic expression can be factored:

Again, the answer is: 5.58257569495584, -3.58257569495584. Here's your graph:
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