One thing to note about the last section is the potential for confusion in connection with the signs of Qs. My recommended approach is described below.
About our tutor
Patrick Andrews has a PhD in Mechanical Engineering from Heriot-Watt University and an MSc in Neuroscience from the University of Cambridge.
A former Chartered Engineer and Chartered Mathematician, Patrick has worked in management consultancies and high-tech startups, and in academia as a postdoc in Applied Mathematics at Cambridge and a maths lecturer at De Montfort University.
Patrick is the father of three delightful (but not uniformly mathematical!) daughters.