STEP workshop 3 - Open Day 2021

Mathematics Open Day 2021 at the University of Cambridge - Andrea, one of our Student Ambassadors, guides participants through the solution to STEP question 11-S2-Q1*, together with Izaak, who's also a Student Ambassador.
* (That's question 1 from STEP 2 in 2011, which you can download from the STEP database at stepdatabase.maths.org/)

[@Vincent-ze8zg]

I am wondering that when sketching the graph like this there are two vertical asymptotes at x=1 and x=-3 .May I ask if I should indicate on the graph?