my teacher changed the bounds of this problem #1 but not on problem #2 when do you know to change the bounds? please help. my test is in 2 hours.
integral (upper bound 4, lower bound 1) dx/ ( (sqrtx) * (2sqrtx +3))
he set u= 2sqrtx +3
consequently du= dx/sqrtx
he then substituted to make the new upper bound 7 and the new lower bound 5.
i understand why he did that, but why didnt he change the bounds in this problem:
integral (upper bound e; lower bound 1) ln(x)dx
he set u=lnx du=dx/x
why did he keep the same (upper bound e; lower bound 1) while he integrated by parts???