Question 131835: How do you solve this so I can understand f(x)=-2x^2+2x+6 Found 3 solutions by stanbon, TakeATuition.com, edjones:Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! How do you solve this so I can understand f(x)=-2x^2+2x+6
You cannot "solve" it when you have two variables.
Maybe this is what you mean.
-2x^2+2x+6 = 0
-2(x^2-x-3) = 0
Divide thru by -2 to get:
x^2-x-3 = 0
Now use the quadratic formula to get:
x = [1 +- sqrt(1 -4*-3)]/2
x = [1 +- sqrt(13)]/2
x = (1+sqrt(13)]/2 or x = (1-sqrt(13))/2
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Cheers,
Stan H.
You can put this solution on YOUR website! f(x)=-2x^2+2x+6
-2(x^2-x-3)
To find the zeroes:
x^2-x-3=0
x^2-x =3
x^2-x+ 1/4=3+ 1/4 complete the square by taking 1/2 the middle term and squaring it.
(x- 1/2)^2=13/4
x- 1/2=+-sqrt(13)/2 sqrt of each side.
x=1/2+-sqrt(13)/2
x=(1+sqrt(13))/2, (1-sqrt(13))/2
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The 2 places the graph crosses the x axis (the x intercepts[where y=0]) also give the answer.
You could also use the quadratic equation.
Ed
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