Me plss whats the answer a b c or d

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

How does a low unemployment rate affect a nation's economy? a. the nation has a higher number of productive resources. b. the nation can spend more money on for unemployed people. c. the nation can save money by paying lower salaries to a large workforce. reset

Amass weighing 16 pounds stretches a spring 8/3 feet. the mass is initially released from rest from a point 2 feet below the equilibrium position, and the subsequent motion takes place in a medium that offers a damping force that is numerically equal to 1/2 the instantaneous velocity. find the equation of motion if the mass is driven by an external force equal to f(t)=cos(2t).