Answer:
8+4√2units
Step-by-step explanation:
The perimeter is the sum of lengths around the triangle that is /AB/+/BC/+/AC/
But the length of the line=√(x2-x1)²+(y2-y1)²
/AB/=√(1-1)²+(-5--1)²=√4²=4units
/BC/=√(5-1)²+(-1--5)²=√16+16=√32=4√2 units
/AC/=√(5-1)²+(-1--1)²=√16=4 units
Perimeter=(4+4√2+4)units=8+4√2 units
