Question 972857: f(x) = -9x2 + 2x + 4. I am having trouble finding an aproximate value for f(x)=0 Found 2 solutions by Boreal, solver91311:Answer by Boreal(15235) (Show Source):
You can put this solution on YOUR website! -9x^2 +2x +4 =0
change all signs to make the square term positive. It is much easier.
9x^2 - 2x - 4=0
quadratic formula
(1/18) [ 2 +/- sqrt (4+144)] a=9 b=-2 4ac=4*(-4)*9
(1/18) 2+/- sqrt (148) ;;sqrt 148=12.17
(2+12.17)/18
14.17/18=0.787
(2-12.17)/18
-10.17/18= - 0.565
Approximate values are -0.565,+0.787
The value of when is exactly . But I'm going to go out on a limb here and guess that you really meant to ask about the values of such that .
Your little bit of ugliness doesn't factor, so your choices are to complete the square (if you are some sort of glutton for punishment) or use the quadratic formula.
Where
, , and
Plug in the numbers and do the arithmetic to find your two values.
By the way, use a caret ("^") mark to indicate raising to a power in plain text. -9x^2 + 2x + 4 means whereas -9x2 + 2x + 4 is just goobledygook.
John
My calculator said it, I believe it, that settles it
