Question

how many real roots does the polynomial 2x^5 + 8x - 7 have?

Answer 1

you know you have 5 solutions (total) because of the 5th power

Answer 2

yes but they are just possible roots--i need REAL roots

Answer 3

look at the graph and see how many times it crosses the x axis or bounces off the x axis

Answer 4

1 only see it cross in one place, means the other 4 are complex

Answer 5

it crosses at (0, -7)?

Answer 6

that is a y intercept and does not count. we are looking at the x intercepts

Answer 7

x=.79540551

Answer 8

but aren't x intercepts on a graph when x=0 (ie on y-axis)?

Answer 9

oh nevermind-- x intercepts are when y=0. right?

Answer 10

yes and I already identified one for you

Answer 11

hmm..i didnt get that--i got .7375?

Answer 12

i used the -b plus/minus the square root of b squared - 4ac all over 2a

Answer 13

can negative numbers be real roots?

Answer 14

can't use that because that is the quadratic formula and you can only use that with a 2nd power, you have a 5th power

Answer 15

then how do find an x-intercept?

Answer 16

have you been taught how to do synthetic division? only way to do this problem

Answer 17

yes i have been taught..but forget!!!

Answer 18

we answered the question, one real root

Answer 19

what equation do you divide by?

Answer 20

i knew the answer was one...i am just confused as to how we got one

Answer 21

in order to do synthetic division, don't we need 2 equtions?

Answer 22

no just a root and a polynomial
what are your instructions because this one only has one real root because it cross the x axis in one place that means that the other 4 are complex solutions

Answer 23

the question is :how many real roots does the polynomial 2x^5 + 8x - 7 have? but i need to show work and be able to explain how i got my answer

Answer 24

well this one is not a nice one to do that with, you can state that it is one solution because it crosses the x axis at x=x=.79540551
since that is not a nice zero to work with (since it is an approximation) then it would not be a good candidate for synthetic division
sorry gotta go

Answer 25

how do u get that answer

Answer 26

@precal

Answer 27

I looked at the graph and used my calculator to find the zero. But if my solution had been a nice whole number or fraction I would have shown you how to use syn division
gotta go, good luck

Answer 28

okay thank you!

Answer 29

still dont get it...
anyehlpe help!!?!?

Answer 30

**anyone

Answer 31

Hey I think I know what you guys are talking about :)) lol

Answer 32

can u explain to me???

Answer 33

@asherwood3