Quadratic equation..

Hi

Can anyone tell me if this is correct

X Sq - 4x - 16 = 0

using

X = -b + Sqrt b sqrd - 4ac / 2a


a =1, b = -4 , C = -16

x = -(-4) Sqrt (-4)sq - 4 x 1 x -16 / 2 x 1

= 4 + - Sqrt 80

= 9 + or minus 8.944/2

+ = 4 + 8.944 = 12.944/2

= 6.472

- = 4 - 8.944 = - 4.944/2

= - 2.472

I apologise in advance for the layout..but know people here are helpful and understanding ..

If this is wrong please tell me where I have gone wrong..thanks :-)

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asked by Leo
  1. Your answers are correct but I don't like the way you typed your solution.
    I am sure on paper it would look better.

    first of all use brackets to avoid problems with order of operation.

    Your first line should have looked like this
    x = (-(-4) Sqrt (-4)sq - 4 x 1 x -16 )/ 2 x 1 , the way you had it only the square root term would have been divided by 2

    in the next line you had
    = 4 + - Sqrt 80
    you dropped the denominator, but then somehow it must have come back in the next few calculations.

    When you use an "=" sign, you are saying,"What I am about to write down next is exactly equal to what I had before".
    Your two lines are not "equal"

    How about this:
    (4 + - Sqrt 80)/2
    = 6.472 or - 2.472

    btw,
    (4 + - Sqrt 80)/2
    =(4 ±4√5)/2
    = 2 ±2√5 , this would be an acceptable answer.

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    posted by Reiny
  2. Thank you for your time and expertise and it does look better on paper ...:-)

    than the way I typed it here

    Thanks again !!!!

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    posted by Leo

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