Posted by Jon on Tuesday, February 19, 2008 at 1:03pm.
Solve 3x^28x+4=0 by graphing. If exact roots cannot be found, state the consecutive integers between which the roots are located.
A)2;between 0 and 1
B)between 0 and 1;between 7 and 8
C)1,2
D)between 0 and 1;between 3 and 4
I don't understand this one either its gotta be A or C I don't undertand what I got from a website which gave me X1=2 and X2=.6 repeating

math  Reiny, Tuesday, February 19, 2008 at 1:28pm
let y = 3x^28x+4 or f(x) = 3x^28x+4 , same thing
try a few x's
I tried 1,0,1,2,3 and y values of
15,4,1,0,7
notice when x = 0 the graph is above the xaxis, but when x=1 the graph is below the xaxis.
So there has to be a solution between x=0 and x=1
Also notice when x=2 , y =0, so x=2 is a solution.
Solutions to equations are where the matching graph cuts the xaxis.
Now that we know that we have an exact solution at x=2, x2 must be an exact factror, and sure enough
3x^28x+4 = (x2)(3x2)
so x=2 or x=2/3

math  Jon, Tuesday, February 19, 2008 at 1:41pm
So C would be the choice?

math  Reiny, Tuesday, February 19, 2008 at 1:59pm
NOOO, it is A
Did you not read when I said:
"notice when x = 0 the graph is above the xaxis, but when x=1 the graph is below the xaxis.
So there has to be a solution between x=0 and x=1
Also notice when x=2 , y =0, so x=2 is a solution. "

math(typo)  Jon, Tuesday, February 19, 2008 at 2:08pm
Oh yeah duh. my mistake
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