NEED HELP WITH ROOTS! WILL MEDAL!
(question following)

Question

NEED HELP WITH ROOTS! WILL MEDAL!
(question following)

studygurl14 · Answer

Find the number of possible positive real roots of
$$f(x)=-6x^4-36x^3+42x^2$$
a) one
b) three
c) two
d) none

studygurl14 · Answer

@Luigi0210 @tkhunny @e.mccormick @iambatman

freckles · Answer

i think you need to apply descartes rule of signs

tkhunny · Answer

Factor factor factor.  Looks like a common $-6x^{2}$ in there.  Factor it out and see what's left.

freckles · Answer

Or actually find the zeros.

studygurl14 · Answer

$$f(x) = -6x^2(x^2+6x-7)$$

studygurl14 · Answer

Isn't there a way to find the answer without actually finding the zeroes?

studygurl14 · Answer

$$f(x) =-6x^2(x+7)(x-1)$$

tkhunny · Answer

Please refer to freckles comment.  However, if it is easy enough to find them, that's probably the way to go.

studygurl14 · Answer

@tkhunny would the answer be two? cause 1 and 0?

studygurl14 · Answer

What is " descartes rule of signs" ?

jdoe0001 · Answer

http://www.youtube.com/watch?v=5YAmwfT3Esc <-- descartes rule of signs

studygurl14 · Answer

Thanks everyone, I think the answer is 2

studygurl14 · Answer

The answer was 1...

tkhunny · Answer

g(x) = x^2 + 6x - 7

DesCartes says 1 Positive Real

g(-x) = x^2 - 6x - 7

DesCartes says 1 Negative Real

You have to get the x = 0 out of there, first.