Rearranging Formulae Where Subject Appears Twice | Algebra | Maths | FuseSchool

In this video we are going to look at how to change the subject of a formula, when the subject appears twice. We have already looked at how to change the subject in another video, so you may want to watch that first. We always use opposites: adding and subtracting, multiplying and dividing, squaring and square rooting. To keep equations balanced, you must do everything to BOTH sides and then cancel on the one side. Take the rearranging step by step, starting with the things that are ‘least’ connected to your chosen subject. When the subject appears twice in the formula, we need to factorise. E.g. Make x the subject of A = 2xy + xz. Factorise the right hand side to get A = x(2y + z) and then divide both sides by the bracket (2 + z), giving A / (2y + z) = x. Another example: make m the subject of F = (mv - mu) / t. Again, because 'm' appears twice we know we’ll probably need to factorise at some point. Start by moving the ‘t’ as that’s least connect to the m’s, so multiply both sides by 't'. Ft = mv - mu. Now factorise the right hand side. Ft = m(v - u). Finish off by dividing both sides by the bracket (v - u), giving the final answer Ft / (v - u) = m. VISIT us at, where all of our videos are carefully organised into topics and specific orders, and to see what else we have on offer. Comment, like and share with other learners. You can both ask and answer questions, and teachers will get back to you. These videos can be used in a flipped classroom model or as a revision aid. Click here to see more videos: Twitter: Access a deeper Learning Experience in the FuseSchool platform and app: Friend us: This Open Educational Resource is free of charge, under a Creative Commons License: Attribution-NonCommercial CC BY-NC ( View License Deed: ). You are allowed to download the video for nonprofit, educational use. If you would like to modify the video, please contact us:

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