SOLUTION: Solve 5x^2 -11x-124=0 using the quadratic equation. I worked it out but not sure if my answer is right

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Question 1190224: Solve 5x^2 -11x-124=0 using the quadratic equation. I worked it out but not sure if my answer is right

Found 3 solutions by Edwin McCravy, math_tutor2020, ikleyn:
Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!

It factors, although you were told to use the quadratic formula.

One of the answers is 31/5.  What's the other one?

(It's a negative integer.)

Edwin

Answer by math_tutor2020(3816) About Me  (Show Source):
You can put this solution on YOUR website!

The given equation is in the form ax%5E2%2Bbx%2Bc=0
We have
a = 5
b = -11
c = -124

They are plugged into the quadratic formula below

x+=+%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29

x+=+%28-%28-11%29%2B-sqrt%28%28-11%29%5E2-4%285%29%28-124%29%29%29%2F%282%285%29%29

x+=+%2811%2B-sqrt%282601%29%29%2F%2810%29

x+=+%2811%2Bsqrt%282601%29%29%2F%2810%29 or x+=+%2811-sqrt%282601%29%29%2F%2810%29

x+=+%2811%2B51%29%2F%2810%29 or x+=+%2811-51%29%2F%2810%29

x+=+%2862%29%2F%2810%29 or x+=+%28-40%29%2F%2810%29

x+=+31%2F5 or x+=+-4

x+=+6.2 or x+=+-4

If you were to plot y+=+5x%5E2-11x-124 (you can use a free tool like GeoGebra or Desmos), then you should find the two x intercepts are exactly 6.2 and -4.

WolframAlpha is another useful tool to check your work. There are many many other free options out there as well.

Answer by ikleyn(52777) About Me  (Show Source):
You can put this solution on YOUR website!
.

On solving quadratic equations using the quadratic formula,  see the lessons
    - Introduction into Quadratic Equations
    - PROOF of quadratic formula by completing the square
in this site.


Also,  you have this free of charge online textbook in  ALGEBRA-I  in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this textbook under the topic  "Quadratic equations".


Save the link to this online textbook together with its description

Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson

to your archive and use it when it is needed.