- #1

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when integrating by substitution, how do i know what to choose as u?

for example

integral of z^2 / (1 + z^3)^(1/3) dz

i am suppposed to choose u as 1+z^3. any other value for u won't give me the right answer. so my question is how do i know what to choose as u? i could have chosen something else but how do i choose the right one?