Algebra investment problem .

Question

An investor kept track of her portfolio profit ,P, at time ,t, measured in years after she began investing .

If P= 4000t^2-28000t+3000 represents her profit, after how many years will she have made $150000

profit?.

Answer 1

P = 4000t^2 - 28000t + 3000

150000 = 4000t^2 - 28000t + 3000

0 = 4000t^2 + 28000t - 147000

Divide both sides by 1000

0 = 4t^2 + 28t - 147

Use the quadratic formula a = 4, b = 28, c = -147

t = -28 + sq rt [(28^2) - (4)(4)(-147)]

2(4)

t = -28 + sqrt[784 + 2352]

8

t = -28 + sqrt[3136]

8

t = -28 + 56

8

t = 3.5 years