How do I find this out without a calculator?

The function f(x)=x^4+2x^3-5 has two real zeros. One is between x=

A.) -2 and -1
B.) -1 and 0
C.) 0 and 1
D.) 1 and 2
E.) 2 and 3

Question

How do I find this out without a calculator?

The function f(x)=x^4+2x^3-5 has two real zeros. One is between x=

A.) -2 and -1
B.) -1 and 0
C.) 0 and 1 
D.) 1 and 2
E.) 2 and 3

anonymous · Answer

plug in the x values
find the pair where one gives a positive result, the other a negative result
then it must be zero somewhere in between

anonymous · Answer

Oh that makes sense so the correct answer would be D?

mathmale · Answer

Erika:  You could easily check your work yourself:  "find the pair where one gives a positive result, the other a negative result; then it must be zero somewhere in between."

Why not evaluate the given function at x=2 and at x=3 and determine whether the results have the same or opposite sides.  If opp, then you could confidently say that you have a zero between 2 and 3.