P(t)=t^4-20t^3-20t^2+1500t+15000

Question

when P is 24000 find t

Answer 1

t^4-20t^3-20t^2+1500t+15000 = 24000
t^4-20t^3-20t^2+1500t - 9000 = 0

There is no practical easy way to solve this equation,
Newton's method would be my way.
I sent it through Wolfram and got

http://www.wolframalpha.com/input/?i=t%5E4-20t%5E3-20t%5E2%2B1500t+-+9000+%3D+0

notice there are 2 real roots, and 2 complex roots.

Are you permitted to use programmable calculators?

Answer 2

sure