From 1990-1994 the mail order sales of health products can be modeled by S= 10t^3+115t^2+25t+2505 where S is the sales (in millions) and t the number of years since 1990. In what year were about $3885 million health products sold.

Answer 1

Let 1990 be 1, 1991 be 2, 1992 be 3, and 1994 be 4
3885=10(3^3)+115(3^2)+25(3)+2505
3885= 270 + 1035 + 75 +2505
3885=3885
1992 is the answer

Answer 2

3885=10t^3+115t^2+25t+2505
−10t3−115t2−25t+1380=0
−5(t−3)(2t2+29t+92)=0
t−3=0 2t2+29t+92=0
t=3
1992