Question 1114937
B(x) = 2300 + 125/x − 517/x^2 for 3 ≤ x ≤ 12
B(6)=2300-125/6+517/36=2300+20.83-14.36=2306.47
B'(x)=-125x^(-2)+2(517)^x^(-3)
=-125/x^2+1034/x^(-3)
B'(6)=1034/216-125/36=+1.315 or $1315 per brush cutter sold
B'(9)=1034/729-125/81=0.287 or $215 per brush cutter sold.
Both are increasing.
{{{graph(300,300,-5,12,-2000,3000,2300+(125/x)-(517/x^2))}}}