SOLUTION: You and your friend part at an intersection. You drive off north at a constant speed, and your friend drives east at a speed that is 6 mph higher. After 2 hours the distance betwee

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Question 787013: You and your friend part at an intersection. You drive off north at a constant speed, and your friend drives east at a speed that is 6 mph higher. After 2 hours the distance between you and your friend is 161.44 miles. You have been driving at _______________mph. (Round to the nearest mile).
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
I am driving at x mph
friend is driving at (x+6) mph
After 2 hours
you have driven 2x miles
your friend 2(x+6) miles
I , my friend and the starting point form a right triangle
Apply Pythagoras theorem
(2x)^2+(2(x+6))^2=161.44^2
4x^2+4(x^2+12x+36)=161.44^2
4x^2+4x^2+48x+144=26062.87
8x^2+48x=26,062.87-144
8x^2+48x-25918.87=0
a= 8 , b= 48 , c= -25918.87

b^2-4ac= 2304 + 829403.84
b^2-4ac= 831707.84
%09sqrt%28%09831707.84%09%29=%09911.98%09
x=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29
x1=%28-b%2Bsqrt%28b%5E2-4ac%29%29%2F%282a%29
x1=( -48 + 911.98 )/ 16
x1= 54.00
x2=%28-b-sqrt%28b%5E2-4ac%29%29%2F%282a%29
x2=( -48 -911.98 ) / 16
x2= -60.00
Ignore negative value
speed 54 mph

m.ananth@hotmail.ca