Answer:
The perimeter is equal to
![16\ units](https://img.qammunity.org/2020/formulas/mathematics/middle-school/f1qio6js5eilpsps568blhc9uuaqsnxgwy.png)
Explanation:
we have that
![A(-1,1),B(2,5),C(5,1)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/wffozfqjh84h8uja155kc87zwxi8kkx1cs.png)
The perimeter of triangle ABC is equal to
![P=AB+BC+AC](https://img.qammunity.org/2020/formulas/mathematics/middle-school/b17c2aup6jerq8501zofznbgzrdnoiarpx.png)
the formula to calculate the distance between two points is equal to
step 1
Find the distance AB
![A(-1,1),B(2,5)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/mr3l130x7pu2eqbba8a21o71bl11zqndz8.png)
step 2
Find the distance BC
![B(2,5),C(5,1)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/nqomkq9s5kgftqst822o297jjmo7qaihlp.png)
step 3
Find the distance AC
![A(-1,1),C(5,1)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/4mhoh57r87neww45fml861b2e2dtyjk8o9.png)
step 4
Find the perimeter
![P=5+5+6=16\ units](https://img.qammunity.org/2020/formulas/mathematics/middle-school/38fv30b13tvykzr3d5u52thet0rgd95nce.png)