MODERATE EXERCISES

(6)

 A girl is at point A on a bank of a straight river which is two miles wide.  
She wants to reach point B, which is across the river and 7 miles downstream, by first 
rowing her boat to a point P on the opposite bank and then walking the remaining distance, 
x, to B.  She can row at 4 miles/hour and walk at 3 miles/hour.  Express the total time T 
that she takes to go from A to B as a function of x.

 

AP2 = 22 + (7 - x)2
AP = (4 + 49 - 14x + x2)1/2
Note: x1/2 = 

T(x) = x/3 + [(53 - 14x + x2)1/2]/4