Aeron Sim's answer to Chua Xiang Ning's Junior College 1 H2 Maths question.

done {{ upvoteCount }} Upvotes
clear {{ downvoteCount * -1 }} Downvotes
Aeron Sim
Aeron Sim's answer
140 answers (Tutor Details)
1st
Hope this helps. :)
Chua Xiang Ning
Chua Xiang Ning
6 years ago
How do you find 3 for the upper and lower integral?
Aeron Sim
Aeron Sim
6 years ago
You see the graph on your GC, you will see that at the lower bound x=2, the graph is in the negative area; f(x) < 0. This means that from x=2 to x=?, I need to integrate -ve f(x) due to the modulus originally.

So this ? Is actually x=3 cos after x=3, the graph is in the positive area already; f(x) > 0. This means that from x=3 to x=p (we know p>3 so p being the upper bound is definitely logically), I need to integrate +ve f(x).

Does my explanation help you understand? Sorry ah I forgot to include an explanation for splitting the modulus into -ve f(x) and +ve f(x).
Chua Xiang Ning
Chua Xiang Ning
6 years ago
I get it now. Thanks for explaining