What is the perimeter of the triangle?

Answer:
D
Step-by-step explanation:
When you add up
[tex](4m^3+2m^2-m)+(4m^2+2m^2-2m)+(7m^3-3m^2+2m)[/tex],
you have [tex]15m^3+m^2-m[/tex],
which is what D is.
Side note:
You only add up the exponents when you multiply.
[tex]4 {m}^{3 } \: + 2 {m }^{2} \: - \: m \: [/tex]
[tex]7 {m}^{3} \: - 3 {m}^{2} + \: 2m[/tex]
[tex]4 {m}^{3} \: + 2 \: {m}^{2} \: - 2m[/tex]
[tex] = (4 {m}^{3} + 2 {m}^{2} - m) + (7 {m}^{3} - 3 {m}^{2} 2m) + (4 {m}^{3} + 2 {m}^{2} - 2m)[/tex]
[tex] = 4 {m}^{3} + 7 {m}^{3} + 4 {m}^{3} + 2 {m}^{2} - 3 {m}^{2} + 2 {m}^{2} - m + 2m -2m [/tex]
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[tex] \huge\green{15 {m}^{3} + {m}^{2} - m}[/tex]