Question

Please help!! State the x-coordinate of the x-intercept in quadrant II for the function below.
f(x)=4x^3-12x^2-x+15

Answer 1

familiar wid Rational root test ?

Answer 2

not really :O

Answer 3

okie, test and see if +1 or -1 are zeroes of given function

Answer 4

so to do that do I just put 1 & -1 into the function?

Answer 5

yup,
usually we use Rational roots theorem + synthetic division to do these. but ok
for now u can simply put +1 and -1 into the function and see if anyone of them give u 0

Answer 6

hey uhh ganeshie8, shouldn't she try 3,5,1,15,-1,-3,-5,-15 aswell?

Answer 7

as per rational root theorem, yes.
lets start wid +1 and -1. if we dont find any 0, then we can test others :)

Answer 8

oh i see what you mean now thanks. I needed the review on this =) you just helped me on my test =))))))

Answer 9

hold on, doing the functions now :)

Answer 10

take ur time :)

Answer 11

for 1 & -1 I got 6 for both functions, did I do that right?

Answer 12

@ganeshie8

Answer 13

Oh it was -1! Thanks :)

Answer 14

nope, for -1 u should get a 0

Answer 15

Yes !

Answer 16

So if I need to find the y-coordinate of the y-intercept for the function f(x)=x^3-9x, how would I go about that?

Answer 17

@ganeshie8

Answer 18

y intercept occurs when x = 0
so simply put x = 0 in given function

Answer 19

f(x)=x^3-9x

put x = 0

0^3-9(0)

0

Answer 20

so y-intercept is 0

Answer 21

so the answer would just be 0?

Answer 22

yup

Answer 23

ohh i see, thank you for taking time to explain it :)

Answer 24

np :)