Question 428032
plane speed in still air		x   		
wind speed		20		
				
against wind x-	10		
with wind x+10		
				
Distance= 500	miles		
				
Time agianst + time with wind =4	hours
t=d/r				
500/(x+20)+500/(x-20)=	4
LCD =	(x-20)(x	+20)				
500*(x-20)+500(x+20)=4
500x-10000+500x+10000=4x ^2-400
1000x=4x ^2-400							
4x^2-1000x-400=0								
Find the roots of the equation by quadratic formula	
a=	4	b=	-1000	c=	-400				
b^2-4ac=	1000000	-	6400										
b^2-4ac=	1006400												
{{{x=(-b+-sqrt(b^2-4ac))/(2a)}}}													
{{{x1=(-b+sqrt(b^2-4ac))/(2a)}}}													
x1=(1000+1003.19	)/8								
x1=	250.4	mph											
x2=(1000-1003.19) /8									
x2=-0.4												
Ignore negative value													
250.4	mph	=speed	in still air