The eighth question is clearly to choose a, here is to find the definite integral of 2x and 0, but 2x and 0 are chosen;

Question 9: Choose D and replace a deformed definite integral with a variable. If tx=u, the upper limit will become s, and the lower limit will still be 0.

And dx = 1/t du, this 1/t is just about 1 with the outside t, and the integrand becomes f(u), that is, the original integral = s (0->; f(u)du。

Obviously, the integral does not depend on t, so choose d.

An integral does not depend on its integral variable, and what letter the integral variable is changed into does not change the value of the integral, so it does not depend on X.