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We know that

(a + b)(a b) = a2 - b2

So

a2 - b2 = (a + b) (a b)

This means that we can factor any expression of the form a2 - b2.


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Question 1/5

1. Factorise 81x2 - 1

(3x + 1)(3x + 1)

(18x + 1)(18x + 1)

(9x + 1)(9x - 1)

(9 + 1)(9x + 1)

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