Proving Definite Integral Using Substitution | Solving Math Problem

[chewy]

Homework Statement

prove by substitution that definite integral int (1/t)dt from [x to x*y] = int (1/t)dt from [1 to y].

Homework Equations

The Attempt at a Solution

i can do this problem if i integrate and use the log laws, no probs, but the question says to use a substitution, I've tried many but to no avail, a push in the right direction would be greatly appreciated. I've asked yesterday about a similar question, which thanks to the forums help i understand. this is the last one on the section and then ill be confident that i can put it rest.

 

[Dick]

Try the obvious, u=t/x.

 

[chewy]

thks very much, I've learned more of these two questions, than the previous easier 30.