Question 432425
Boat speed		x   		
current speed 		8		
				
against current	x-8 mph		
with current	x+8	mph	
				
Distance= 	19	miles		
				
Time against + time with wind = 9 hours
t=d/r			
...
19/(x +	8)+19/(x-8)=9				
																	
LCD =(x-8)(x+8)		
19*(x -	8)+19x+	8)=9				
19x-152+19x+152	=9(x ^2	-64)
38x=9x ^2-576											
9x ^2-38x-576=0								
Find the roots of the equation by quadratic formula			
a=	9	b=	-38	c=	-576				
b^2-4ac=	1444	+	20736					
b^2-4ac=	22180	:sqrt(22180)=148.93										
{{{x=(-b+-sqrt(b^2-4ac))/(2a)}}}					
{{{x1=(-b+sqrt(b^2-4ac))/(2a)}}}						
x1=(38+148.93)/18												
x1=10.38 mph																
x2=(38	-148.93	) /	18													
x2= -6.16 ( ignore negative)
speed = 10.38 mph