Speed, S = Distance (d) / Time (t) => S= d/t => t= d/S
Let the speed of boat in still water be x mph
Resulting speed upstream = x-4 mph for a distance of 30 miles
Resulting speed downstream = x-4 mph for a distance of 50 miles
Time taken in both distances is equal.
Therefore,
30/(x-4) = 50/(x+4) => 30(x+4) = 50(x-4) => 30x+120 = 50x-200 => 120+200 = (50-30)x => 20x = 320 => x=320/20 = 16 mph
The speed of boat in still water is 16 mph.
10(4^2-(9)
Since 16-9 is 7
And 10 times 7 is 70
The fourth vertex would be at point (-9,1).
The slope from (5,-4) to (3,4) is -8/2 or -4.
So I did that with (-7,-7) to the fourth vertex to get the answer.
