Im trying to integrate this, using theorem 7.9 of apostol's book:
$$\int^{10}_0 f(x)d\alpha(x) $$
$f(x) = x^2$ and $\alpha(x)= 3\chi(7,9](x)$ Where $\chi(x)$ is $0$ everywhere except $1$ in the interval $(7,9]$
So using this theorem, and knowing the steps are at 7, and 9, and everywhere else the sum and substraction of $\alpha$ is $0$ i get:
$$f(7)[\alpha(7+)-\alpha(7-)] + f(9)[\alpha(9+)-\alpha(9-)] = $$ $$= 7^2 (3*(1 - 0)) + 9^2 (3*(0-1)) = 3*7^2 - 3*9^2$$
Does this sound about right? In class we did a mostly theeoretical stuff with the R-S integral but not a single example so I'm i little lost.
