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Question 87372: i cant figure out thi problem and as wondering if you could help me out on it.
f[x]=-xSq.+9x-5 there is four answers a[-9over2,-263over4] b[9,5 ] c[9over2,61over4] d[9over2,101over4] i think it might be c but iam stuck
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! [x]=-xSq.+9x-5 there is four answers a[-9over2,-263over4] b[9,5 ] c[9over2,61over4] d[9over2,101over4] i think it might be c but iam stuck
:
f(x)= x^2 + 9x - 5
To solve, using the "complete the square" method:
x^2 + 9x - 5 = 0
x^2 + 9x + __ = +5
:
Find the term which will make it a perfect square;
Divide coefficient of the 2nd term by 2 and square it
Here, that would be (9/2)^2 = (81/4), add this to both sides
x^2 + 9x + (81/4) = +5 + (81/4)
:
x^2 + 9x + (81/4) = (20/4) + (81/4); (5 = 20/4)
x^2 + 9x + (81/4) = 101/4
:
Which is:
(x^2 + 9/2)^2 = 101/4
Find the square root of both sides:
x + (9/2) = +/-sqrt(101/4)
x = 
:
The closest answer would be d, but it should be a minus 9/2.
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