Quadratics: Factorising, completing the square and graphs

I am looking at factorising with year 9 after half term and I have been thinking about starting the lesson with the following task. I know they have looked at rectangles regularly at KS2 and KS3 and our next unit after the current one is on 2D shapes. I thought this activity would give them a good starting point to start factorising quadratic by inspection.