Question 519213
speed	x		
speed	x	-	3
			
Distance = same		90	miles
original time – time with increased speed =1			
t=d/t			
90/x-90	/(x+3)	=1				
LCD= 	x(x+3	)										
multiply by LCD																
90(x+3)-90x=x(x	+3)
90x+270-90x=X^2	+3x				
270	=	1	x^2	+	3	x										
x^2		+	3	x	-	270	=	0							
																
a=	1		b=	3		c=		-270								
																
x1=(-3+sqrt(9-(-1080))/	2					
=	1089															
x1=	15															
																
x2=(3-sqrt(9-(-1080))	/	2					
																
x2=	-18

ignore negative

speed = 15 mph

m.ananth@hotmail.ca