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

Question

.sam. · Answer

you sure is +84 or -84?

anonymous · Answer

I think it's +

.sam. · Answer

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

anonymous · Answer

ok :) thanks

.sam. · Answer

$$-7x^4+49x^3-84x^2$$
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

amistre64 · Answer

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

amistre64 · Answer

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

amistre64 · Answer

..and obama ate a dog :/