Suppose that \(f\) and \(g\) are integrable on \([a, b]\), then \(f+g\) is integrable on ......... .
Suppose that \(f\) and \(g\) are integrable on \([a, b]\), then \(f+g\) is integrable on ......... .
\((a, b)\)
Cannot comment
\([a, b]\)
Range of \(f+g\)
Solution
As \(f\) and \(g\) are integrable on \([a, b]\), then \(\int_{x_1}^{x_2} f(x) d x\) and \(\int_{x_1}^{x_2} g(x) d x\) exists for every value of \(x_1, x_2 \in[a, b]\), then \(\int_{x_1}^{x_2} f(x) d x+\int_{x_1}^{x_2} g(x) d x=\int_{x_1}^{x_2}(f+g)(x) d x\)
Also exists for \(\forall x_1, x_2 \in[a, b]\) Hence, option (c) is correct.