Question 144572
60/(x-3)+60/(x+3)=9
[60(x+3)+60(x-3)]/(x-3)(x+3)=9
(60x+180+60x-180)/(x^2-9)=9
120x=9x^2-81
9x^2-120x-81=0
Using the quadratic equation:{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}we get:
x=(120+-sqrt[-120^2-4*9*-81])/2*9
x=(120+-sqrt[14,400+2,916])/18
x=(120+-sqrt17,316)/18
x=(120+-131.59)/18
x=(120+131.59)/18
x=251.59/18
x=13.98 MPH for the speed of the boat.
proof
60/(13.98-3)+60/(13.98+3)=9
60/10.98+60/16.98=9
5.4645+3.5336=9
9~9