Since three vertices are given, the figure must be a triangle. To find the perimeter, you must find the lengths of all three sides and add them up. The lengths can be found using the distance formula:
d = √[(x2 - x1)2 + (y2 - y1)2]
The lengths of the three sides using this formula are:
DE = √34
EF = √13
DF = √34 .
Thus, the perimeter is P = 2√34 + √13 . Notice that the triangle is isosceles since two of the sides have equal lengths.
If you need a decimal answer, you should use a calculator.