Acar rental is 40$ per day plus $0.30 per mile traveled write the equation as a function

Enter the number of complex zeros for the polynomial function f(x) = x 4+ 5x² +6

[10 points, algebra 2-simplifying complex fractions]according to my answer key the restrictions are -1 and 4. but why not positive 1?

41/17 as a decimal rounded to the nearest hundredth