SOLUTION: I am looking at an example of a quadratic equation x^2 - 4x - 7 =0 using the quadratic formula I come up with 4 (+or-)(-4^2-4(1)(-7))/2 the instructor simplified this to x = 4(

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: I am looking at an example of a quadratic equation x^2 - 4x - 7 =0 using the quadratic formula I come up with 4 (+or-)(-4^2-4(1)(-7))/2 the instructor simplified this to x = 4(      Log On


   

Question 335690: I am looking at an example of a quadratic equation x^2 - 4x - 7 =0
using the quadratic formula I come up with 4 (+or-)(-4^2-4(1)(-7))/2 the instructor simplified this to x = 4(+or-)2(11^1/2) I don't see where the number 11 came from or how the 2 was pulled out of the square can someone explain. I will have a similar question to this according to the teacher in a quiz next week and I need to understand this. Thank-you.
Found 2 solutions by Fombitz, stanbon:
Answer by Fombitz(32388) About Me  (Show Source):
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
quadratic equation
x^2 - 4x - 7 =0
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a = 1 ; b = -4 ; c = -7
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x = [-b +- sqrt(b^2-4ac)]/(2a)
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x = [4 +- sqrt(16-4*1*-7)]/(2*1)
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x = [4 +- sqrt(16+28)]/2
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x = [4 +- sqrt(44)]/2
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x = [4 +- sqrt(4*11)]/2
----\
x = [4 +- 2*sqrt(11)]/2
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x = [2 +- sqrt(11)]
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x = 2+sqrt(11) or x = 2-sqrt(11)
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Cheers,
Stan H.