Use Descartes rule to determine the possible number of positive and negative solutions for the polynomial: f(x)=10x^4-21x^2+11

Raymond just got done jumping at super bounce trampoline center. the total cost of his session was $43.25 . he had to pay a $7 entrance fee and $1.25 for every minute he was on the trampoline. write an equation to determine the number of minutes (t) that raymond was on the trampoline.