SOLUTION: This word problem needs to be solved using a rational expression, thank in advance for the help. The current of a river is 2 miles per hour. A boat travels to a point 8 mile upst

Question 147599This question is from textbook
: This word problem needs to be solved using a rational expression, thank in advance for the help. The current of a river is 2 miles per hour. A boat travels to a point 8 mile upstream and back again in 3 hours. What is the speed of the boat in still water? This question is from textbook

Answer by scott8148(6628) (Show Source): You can put this solution on YOUR website!
let x=speed of boat

d=rt __ t=d/r __ total time = time upstream + time downstream

3=[8/(x+2)]+[8/(x-2)] __ multiplying by (x+2)(x-2) __ 3x^2-12=16x

3x^2-16x-12=0 __ factoring __ (3x+2)(x-6)=0

3x+2=0 __ subtracting 2 __ 3x=-2 __ dividing by 3 __ x=-2/3 __ negative value not realistic

x-6=0 __ adding 6 __ x=6
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