SOLUTION: I have the following quadratic equation that I have been trying to graph for like an hour and I am having the toughest time with it. Could someone please help me ASAP??? Thanks

Algebra ->  Graphs -> SOLUTION: I have the following quadratic equation that I have been trying to graph for like an hour and I am having the toughest time with it. Could someone please help me ASAP??? Thanks      Log On


   

Question 145839: I have the following quadratic equation that I have been trying to graph for like an hour and I am having the toughest time with it. Could someone please help me ASAP???
Thanks!
Maggie
3x2(squared)-x-1 = 0
Could you provide each step so that I may see where I have messed up. I know that I need to have ax2 + bx - c =0, so a=3, b=-1 and c=-1.
I've have plugged these into the -b +/- b2-4ac over 2a???? But for some reason, I get screwed up about mid way through.
Help!!!
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
You don't need to use the quadratic formula to graph this.

In order to graph f%28x%29=3x%5E2-1x-1, we need to plot some points. To do that, we need to plug in some x values to get some y values


So let's find the first point:



f%28x%29=3x%5E2-1x-1 Start with the given function


f%28-2%29=3%28-2%29%5E2-1%28-2%29-1 Plug in x=-2


So when x=-2, we have y=13


So our 1st point is (-2,13)


-------------- Let's find another point --------------


f%28x%29=3x%5E2-1x-1 Start with the given function


f%28-1%29=3%28-1%29%5E2-1%28-1%29-1 Plug in x=-1


So when x=-1, we have y=3


So our 2nd point is (-1,3)


-------------- Let's find another point --------------


f%28x%29=3x%5E2-1x-1 Start with the given function


f%280%29=3%280%29%5E2-1%280%29-1 Plug in x=0


So when x=0, we have y=-1


So our 3rd point is (0,-1)


-------------- Let's find another point --------------


f%28x%29=3x%5E2-1x-1 Start with the given function


f%281%29=3%281%29%5E2-1%281%29-1 Plug in x=1


So when x=1, we have y=1


So our 4th point is (1,1)


-------------- Let's find another point --------------


f%28x%29=3x%5E2-1x-1 Start with the given function


f%282%29=3%282%29%5E2-1%282%29-1 Plug in x=2


So when x=2, we have y=9


So our 5th point is (2,9)


Now lets make a table of the values we have calculated 



 xy



 -213
 

 -13
 

 0-1
 

 11
 

 29
Now plot the points



Now connect the points to graph y=3x%5E2-1x-1 (note: the more points you plot, the easier it is to draw the graph)