This might be a bit long.
I'm assuming you're trying to find the length of the median. ^_^
Draw a graph and mark the points you're given.
R = <3, 3>
S = <-1, 6>
T = <1, 8>
Median: a line that goes from a vertex of a triangle and bisects (cuts in half) the opposite side.
On your graph, draw the median from point R to X ( which is the center of the line ST ). To find X, find the midpoint between S and T; you can find this by finding the respective midpoints of the x- and y-components.
S x = -1, T x = 1, Midpoint x = 0
S y = 6, T y = 8, Midpoint y = 7
X = <0, 7>
To find the length of the line, use the Pythagorean Theorem: a 2 + b 2 = c 2, where c is the hypotenuse and a and b are the legs. In this case, imagine a triangle formed between R=<3,3> and X=<0,7>, with the third point at <0,3>. This creates a right triangle, with two legs of lengths 3-0=3 and 7-3=4. 3 2 + 4 2 = c 2, then find c.
This particular right triangle is a special case, because three squared plus four squared equals exactly five squared. In math stuff: 3 2 + 4 2 = 5 2. This means that the length of RX is five.
^_^ Hope this helps!
