Question

7. (a) (1 + a - b)(1 - a +b)
(c) (5x + 6y - 1)(5x – 6y - 1)​

Answer 1

Step-by-step explanation:

$(1 + a - b)(1 - a + b) \\ = 1(1 - a + b) + a(1 - a + b) - b(1 - a + b) \\ = 1 - a + b + a - {a}^{2} + ab - b + ab - {b}^{2} \\ = 1 - {a}^{2} - {b}^{2} + 2ab$

$(5x + 6y - 1)(5x - 6y - 1) \\ = 5x(5x - 6y - 1) + 6y(5x - 6y - 1) - 1(5x - 6y - 1) \\ = 25 {x}^{2} - 30xy - 5x + 30xy - 36 {y}^{2} - 6y - 5x + 6y + 1 \\ =25 {x}^{2} - 10x - 36 {y}^{2} + 1$

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