The perimeter of triangle ABC is 18.9 units
The perimeter of a triangle is calculated by adding all the sides together.
To get the perimeter we have to find the side lengths.
AB = √ 9-1)² + 2-1)²
AB = √8² + 1²
AB = √65
= 8.1 units
BC = √9-4)² + 5-2)²
= √5² + 3²
= √25+9
= √34
= 5.8
AC = √ 4-1)² + 5-1)²
AC = √3² + 4²
AC = √ 9+16
AC = √25
= 5
Perimeter = 8.1 + 5.8 + 5
= 18.9 units