need help with thiss

There are 10 sides that are equal to [tex]2a^{3} +a^{2} - a[/tex], and 2 sides equqal to [tex]4a^{4}[/tex]
Perimeter : [tex]20a^{3} + 10a^{2} - 10a + 8a^{4}[/tex]
Hello!
10 (2a³ +a² -a) + 2 ( 4a^4)
= 20a³ + 10a² -10a + 8a^4
= 8a^4 +20a³ -10a² -10a