What substitution should be used to rewrite 4x^4-21x^2+20=0 as a quadratic equation

Nell has a sales clerk job that pays $12 per hour for regular gas work hours. she gets double time for any hours over 40 that she works in a week. how many hours did nell work if her weekly pay was $744

Simplify a7/a4 a) 1/a3 b)-a/a2 c)a4/a3 d)a3

Trish receives $450 on the first of each month. josh receives $450 on the last day of each month. both trish and josh will receive payments for next four years. at a discount rate of 9.5 percent, what is the difference in the present value of these two sets of payments?