Which of the following is the graph the function f(x) = 3x^3 + 9^2 - 2x + 3 ?

Question

anonymous · Answer

I think the answer is either A or C, someone please help

e.mccormick · Answer

Well, if x=0, then all the terms but the last go by by.  So 0,3 must be on the graph.

e.mccormick · Answer

THat alone eliminates everything other than A and D.  So all you need to do is pick one other easy test point and you can confirm.

e.mccormick · Answer

I would try x=1, cause then you do not really need to figure out much, and presto, second y value to check.

With many of these types of questions, that is all you need to do.  Find x=0 and x=1.  It generally eliminates most of the graphs.

anonymous · Answer

how would you do x=1? would you just substitute 1 in for all the x's and then solve it?

e.mccormick · Answer

Yep.  So you just end up with the numbers.

e.mccormick · Answer

When x=0, every factor with an x dissapears.  That is why x=0 is easy.  For x=1, the x does not matter and you just add and subtract the constants.

e.mccormick · Answer

And I am assuming you typoed the 9^2 and it is supposed to be 9x^2.

anonymous · Answer

it just shows as 9^2 not 9x^2

e.mccormick · Answer

Hmmm... that is probably a mistake, because NONE of the graphs are for it with 9^2 = 81.  But one of them is for it with 9x^2.

anonymous · Answer

yeah, i think it was a mistake. i just checked again and got A as my final answer, is this correct?

e.mccormick · Answer

Yes.  Cause when x=1 it would be 13.  If yo look at (0,3) and (1,13) thy would only show up on graph A.

anonymous · Answer

thank you so much! :)

e.mccormick · Answer

np.  Have fun, and no you know an easy way to do those.  =)