71 b)(2a b) b2 C1 2 C1 for showing all the possibilities H (2a + + = 4a2 + 4ab + b)(2a b) b2 (2a + = 4a2 – – b)(2a b) b2 (2a = 4a2 + – – –4ab C1 C1 for showing all the possibilities b)(a b) a2 b2 (a + + = + 2ab + b)(a b) a2 b2 (a + = – – b)(a b) a2 b2 (a = 2ab + – – – C1 C1 for clear explanation The difference in the two is that in the b) a2 ab (2a ± product, both the and terms have a coefficient of 4 (when the ab b) term is not zero), but in the (a ± a2 product, the term has a coefficient 3 ab of 1 and the term has a coefficient ab of 2 (when the term is not zero).
71 (2a + b)(2a + b) = 4a2 + 4ab + b2 (2a + b)(2a – b) = 4a2 – b2 (2a – b)(2a – b) = 4a2 –4ab + b2 (a + b)(a + b) = a2 + 2ab + b2 (a + b)(a – b) = a2 – b2 (a – b)(a – b) = a2 – 2ab + b2 The difference in the two is that in the (2a ± b) product, both the a2 and ab terms have a coefficient of 4 (when the ab term is not zero), but in the (a ± b) product, the a2 term has a coefficient of 1 and the ab term has a coefficient of 2 (when the ab term is not zero). C1 C1 C1 2 C1 for showing all the possibilities C1 for showing all the possibilities C1 for clear explanation H 3
Higher_Skills_Algebra_MarkScheme_Edexcel.docx