Question 543154
Helicopter 	speed	x   	mph	
wind 	speed	20	mph	
				
against 	wind 	x-	20	mph
with 	wind 	x+	20	mph
				
Distance= 	30	miles		
				
Time against + time with  = 			0.8	hours
t=d/r				

30	/(	x   	+	20	)	+	30	/(x	-	20	)	=	0.8				
																	
LCD =	(x	-	20	)	(	x   	+	20	)								
30	*(	x   	-	20	)	+	30	(x	+	20	)	=	0.8				
30	x   	-	600	+	30	x   	+	600		=	0.8	(	x ^2		-	400	)
60	x   	=	0.8	x ^2	-	320											
0.8	x ^2	-	-60	x   	-	320											
																	
Find the roots of the equation by quadratic formula																	
																	
a=	0.8	,	b=	-60	,	c=	-320										
																	
b^2-4ac=	3600	+	1024														
b^2-4ac=	4624		{{{	sqrt(	4624	)=	68	}}}									
{{{x=(-b+-sqrt(b^2-4ac))/(2a)}}}																	
{{{x1=(-b+sqrt(b^2-4ac))/(2a)}}}																	
x1=(	60	+	68	)/	1.6												
x1=	80																
x2=(	60	-68	) /	1.6													
x2= 	-5																
Ignore negative value																	=	80	mph		speed	

m.ananth@hotmail.ca