Answer:
47.
Step-by-step explanation:
1) the rule:
[tex]f_{avr}=\frac{1}{b-a} \int\limits^b_a {f(x)} \, dx ,[/tex]
where a;b are 0 and 12, f(x)=x²-1.
2) according to the rule above:
[tex]f_{avr}=\frac{1}{12-0} \int\limits^{12}_0 {(x^2-1)} \, dx=\frac{1}{12}(\frac{x^3}{3}-x)|^{12}_0=48-1=47.[/tex]
