Question 534938
first part	90	miles										
second part	80	miles										
												
speed in first part	x			mph								
speed second part	x		-5	mph								
Total rowing time		2	hours									
Time first part		90	/	x								
Time second part		80	/	(	x	-5	)					
												
Time first part + time second part =			4	hours								
												
90	/	x				+	80	/(x	-5	)	=	2
LCD =	(	x	+	0	)*	(x	-5	)				
multiply the equation by the LCD												
we get												
90	*	(x	-5	)+	80		x				=	2
90	x	-450	+	80	x				=	2	X^2	
180	x	-450	=	2	X^2							
2	X^2	-180	x	450			=	0				
2	X^2+	-180	x+	450	=							
/	2											
1	X^2	-90	x	225	=				
Find the roots of the equation by quadratic formula				
a=	1	b=	-90	c=	225				
b^2-4ac=	8100	-	-900									
b^2-4ac=	7200

{{{sqrt(	7200	)}}}=	84.85
					
{{{x=(-b+-sqrt(b^2-4ac))/(2a)}}}												
{{{x1=(-b+sqrt(b^2-4ac))/(2a)}}}												
x1=(	90	+	84.85	)/	2							
x1=	87.43		87 3/7									
x2=(	90	-84.85	) /	2								
x2= 	2.57		2 4/7									
Ignore negative value												
x	=	87.43	mph	LCD =		speed						
												
CHECK												
Time first part	+	Time second part										
1.03	+	0.97	=	2								
												
												
m.ananth@hotmail.ca