We have three points that represent the vertices of the triangle
- A( -1, 5 )
- B( 4, 5 )
- C( -1, 1 )
We need to calculate the distances between the points to calculate the perimeter
To calculate the distances we must use the next equation
![d=\sqrt[]{(x_2-x_1)^2+(y_2-y_1)^2}](https://img.qammunity.org/2023/formulas/mathematics/college/be685jmxw05hm2tq94m5iuge2xjynn1hfn.png)
Distance for AB:
![\begin{gathered} d_1=\sqrt[]{(4-(-1))^2+(5-5)^2} \\ d_1=\sqrt[]{5^2+0^2}=\sqrt[]{5^2}=5 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/32adc4fl972dsyt0igbuowe69u05hzokl0.png)
Distance for BC:
![\begin{gathered} d_2=\sqrt[]{(-1-4)^2+(1-5)^2} \\ d_2=\sqrt[]{(-5)^2+(-4)^2}=\sqrt[]{41} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/pq1ogyik3rpzpwtbu4a8m7o6avh914bkor.png)
Distance for AC:
![\begin{gathered} d_3=\sqrt[]{(-1-(-1))^2+(1-5)^2} \\ d_3=\sqrt[]{0^2+(-4)^2}=\sqrt[]{16}=4 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/9kxj0d9oblq9il97xqf9h9m5zy99u2legx.png)
Finally, the perimeter is
![\begin{gathered} S=d_1+d_2+d_3 \\ S=5+\sqrt[]{41}+4 \\ S=9+\sqrt[]{41} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/i1xiyn4p82fx93m13197naw4yhs81ar2mo.png)
So, the answer is
![9+\sqrt[]{41}\text{ units}](https://img.qammunity.org/2023/formulas/mathematics/high-school/nt6gvrk6h8jl8lkr1102h82guy0v8bb04y.png)