For 1980 through 1996, the total exports E (in billions of dollars) of the United States can be modeled by E = -0.013t3 + 5.033t2 – 23.2t + 233 where t is the n

Question

For 1980 through 1996, the total exports E (in billions of dollars) of the United States can be modeled by E = -0.013t3 + 5.033t2 – 23.2t + 233 where t is the number of years since 1980. In what year were the total exports about $312.76 billion?

Answer 1

You must solve the equation E = 312.76.

 

-0.013t³ + 5.033t² - 23.2t + 233 = 312.76, or

 

-0.013t³ + 5.033t² - 23.2t - 79.76 = 0.

 

The best way to do this is to graph the left side with a graphing calculator and locate the zeros (roots). 

 

I will leave the rest to you.