A^2+B^2=C^2
18^2+80^2=C^2
324+6400=C^2
6724=C^2
*Squareroot*
82=C
D(7, 3), E(8, 1), and F(4, -1)
We calculate the squared distances between the points:
Since 
we have a right triangle with hypotenuse DF.
The slope of the first equation has a slope of one and a y intercept of -4. The second equation has a y intercept of -2.3333 as seen when plugging in 0 for x, so the same y-intercept and same line are out of the question. This means either they have the same slope and thus are parallel or intersect at some point. A simple way to find out? Plug in 1 for x on the second. If it isn't -1.33333, which is a slope of positive 1 such as in the first equation, they WILL INTERSECT somewhere. When plugging in 1, we get
3y - 1 = -7
3y = -6
y = -2
(1, -2) is the next point after (0, -2.3333)
That means it is most certainly not the same slope, and thus they will intersect at some point. The two slopes are 1/1 and 1/3 if you weren't aware.
