<PRE><B>Question 875628</B>
going	speed	x					
returning	speed	x	+	15			
							
	Distance = same		40	miles	0.5		
	original time – time with increased speed =					0.5	hour
	t=d/t						

40	/	x	-	40	/	(	x	+	10	)	=	0.5				
LCD=	x	(	x	+	15	)										
multiply by LCD																
40	(	x	+	15	)	-	40	x	=	0.5	x	(	x	+	15	)
40	x	+	600	-	40	x	=	0.5	X^2	+	7.5	x				
600	=	0.5	X^2	+	7.5	x										
0.5	X^2		+	7.5	x	-	-600	=	0							
Find roots of the quadratic equation																
a=	0.5		b=	7.5		c=	-600									
																
x1=	(	-7.5	+	sqrt(		56.25	-	1200	))	/	1					
x1=(	-7.5	+	35.44	)/	1											
x1=	27.94															
																
x2=	(	-7	-	sqrt(		49	-	20	)	/	2					
x2=(	-7.5	-	35.44	)/	1											
x2=	-42.94															
ignore negative

going speed was 27.94 mph

add 15 for returning speed</PRE>