Question

Find the number of positive real zeros of f(x)=-7x^4+49x^3+84x^2

Answer 1

you sure is +84 or -84?

Answer 2

I think it's +

Answer 3

if + you cant get the roots, i'll just assume its -

Answer 4

ok :) thanks

Answer 5

\[-7x^4+49x^3-84x^2\]
Factor the x^2 out

\[x^2(-7x^2+49x-84)\]
\[x^2(x-3)(x-4)\]
Set it =0 to find the roots,
\[(x^2)(x-3)(x-4)=0\]
Set each brackets =0,
x^2=0 x-3=0 x-4=0
x=0 x=3 x=4

Answer 6

the descartes rule of signs gives us that there is 1 positive root since ther eis only 1 sign change in the eqs positive position

Answer 7

its not asking for the roots; just the number of roots that are positive in value

Answer 8

..and obama ate a dog :/