find the length of the third side, If necessary round to the nearest tenth

Step-by-step explanation:
[tex] {12}^{2} + {9}^{2} = {a}^{2} \\ 144 + 81 = {a}^{2} \\ {a}^{2} = 225 \\ a = 15[/tex]
Answer:
a = 15
a = - 15
Step-by-step explanation:
Exponentiation
12² + 9² = a²
144 + 9² = a²
so a equal to 15, -15