Question

I need help with #8. I need to use the quadratic formula. I have a calculator that is programmed for the quadratic formula so all I need are the a, b, and c values. for this problem, I am required to show any equations used to solve for the variable. hope you can help me, thanks!!​

Answer 1

x = 14

Explanation:

Extend line AB so that it intersects ray CE at point G. Then angles BGC and BAD are "alternate interior angles", hence congruent.

The angle at B is exterior to triangle BCG, and is equal to the sum of the interior angles at C and G:

138 = (376 -23x) +(x^2 -8x)

Subtracting 138 and collecting terms we have ...

x^2 -31x +238 = 0

For your calculator, a=1, b=-31, c=238.

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Additional comment

You will find that the solutions to this are x = {14, 17}. You will also find that angle BCE will have corresponding values of 54° and -15°. That is, the solution x=17 is "extraneous." It is a solution to the equation, but not to the problem.

For x=14, the marked angles are A = 84°, C = 54°.