Question

factorise
$(a + b) ^{2} - 9c^{2}$
​

Answer 1

Answer:

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Step-by-step explanation:

Applying the identities:

a^2−b^2 = (a+b) (a−b) and (a+b)

2

=a

2

+b

2

+2ab

Using the above identities, the equation a

2

+2ab+b

2

−9c

2

can be factorised as follows:

a

2

+2ab+b

2

−9c

2

=(a+b)

2

−9c

2

=(a+b)

2

−(3c)

2

=(a+b+3c)(a+b−3c)

Hence, a

2

+2ab+b

2

−9c

2

=(a+b+3c)(a+b−3c)