Eric Nicholas K's answer to Kathy's Secondary 4 A Maths Singapore question.

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Eric Nicholas K
Eric Nicholas K's answer
5997 answers (Tutor Details)
1st
Here the terms are simple enough so there is no need for substitution u. In more complicated expressions like 2(e^x)^2 - 4(e^x) + 2 = 0, letting u = e^x makes things easier to see.