Question 643417
two boats leave port at the same time, one east and one south (90 degree angle)
the eastbound boats speed is 2mph greater than the southbound boats speed. after 9 hours the boats are 90 miles apart. what is the southbound boats speed?
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let x=speed of southbound boat
x+2=speed of eastbound boat
After 9 hours:
southbound boat traveled 9x miles
eastbound boat traveled 9(x+2) miles
..
draw a right triangle with legs 9x and 9(x+2) and hypotenuse=90 
by pythagorean theorem:
(9x)^2+[9(x+2)]^2=90^2
81x^2+81(x^2+4x+4)=8100
divide by 81
x^2+x^2+4x+4=100
2x^2+4x-96=0
divide by 2
x^2+2x-48=0
(x+8)(x-6)=0
x=-8 (reject,x>0)
x=6
speed of southbound boat=6 mph