Let .

Note that for large, negative x f(x) takes a positive value.

f(0)= -9 is negative. Thus there is at least one root between a large negative x and x = 0.

For large, positive x f(x) takes a positive value again. Thus there is at least one root between x = 0 and large a large positive x.

Thus there are at least 2 real roots.

-Dan