Question

the value -1 is a lower bound for the zeros of the function f(x)=x^4+x^3-11x^2-9x+18

Answer 1

Plug in -1 into your function and first check to see if it a zero.

If f(-1) = 0, then you can try to see if that's the lower bound of the zeroes for the function. But if you don't get zero when you plug in -1, then that means that the value -1 isn't even a bound for the zeroes of that function.