Substituting Integration technique for multi choice?

[chickenpop]

I'm stuck on this question, where you have to substitute 'u' to manipulate the integral. What I don't understand is how do we know what to substitue? Say we use 4-3x instead of, root(4-3x), wouldn't that give a different answer and waste valuable time in exams?

[shinny]

Heh, Dr. G? I still recognise his handwriting and his test layout after 2 years =P

Well anyway, once you do more substitution questions, you'll get the hang of the best substitutions to make. Remember, these will be MCQ so you can look at the structure of the answers to gauge roughly what sort of substitution to make, but still in general, they will always choose the most efficient path.

[TrueTears]

Also remember, if you really don't know what to substitute, use your calculator, practise typing in fast and check the multiple choice and see which intergral outputs the same answer.

[tram]

Also remember, if you really don't know what to substitute, use your calculator, practise typing in fast and check the multiple choice and see which intergral outputs the same answer.

LOL, when all else fails, just bash it out with the caculator, srsly, that what it's there for

[TrueTears]

lol yeh, the calculator is ur best friend in the exam, master it, u dono how important it is sometimes.

even tho im not a fan of using the calculator but for vce's sake u rly need to know how to fully utilise it

[Mao]

Look at the intervals. Initially you have -1 to 1, after the substitution you have 1 to rt[7], that square root says you're going to have to substitute a square root function.

[tram]

lol yeh, the calculator is ur best friend in the exam, master it, u dono how important it is sometimes.

even tho im not a fan of using the calculator but for vce's sake u rly need to know how to fully utilise it

precisely this

[chickenpop]

Heh, Dr. G? I still recognise his handwriting and his test layout after 2 years =P

Well anyway, once you do more substitution questions, you'll get the hang of the best substitutions to make. Remember, these will be MCQ so you can look at the structure of the answers to gauge roughly what sort of substitution to make, but still in general, they will always choose the most efficient path.

yep, Dr G lol