7#
大 中
小 發表於 2018-2-14 04:42 PM (第 369 天)
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for the first question
1. find dx in terms of du
2. find new upper and lower limit
3. sub x by 1/u
4. change upper lower limit
5. use prop. of log to remove power -1 of u in ln u
6. rewrite denominator into one fraction
7. cancel out u^2
8. change each u to x (prop.of integration)
9. (integral after 4.)=(integral after 8.)
10. 2(given integral) = 0
11. proved