Question

81-9a^2-12ab-4b^2 factorise

Answer 1

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Here is u r Ans ➡

$= 81 - 9a {}^{2} - 12ab - 4a {}^{2}$


$= 81 - (9a {}^{2} + 12ab + 4b {}^{2} )$

$= using > a {}^{2} + 2ab + b {}^{2} = (a + b) {}^{2}$

$= 81 - (3a + 2b) {}^{2}$

$= using \: > \: a {}^{2} - b {}^{2} = (a - b)(a + b)$

$= (9 - (3a + 2b)) \times (9 + (3a + 2b))$

$= (9 - 3a - 2b) \times (9 + 3a + 2b)$
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Answer 2

Answer:

[9 - (3a + 2b)] [9 + (3a + 2b)]

Step-by-step explanation:

81 - 9a ^ 2 - 12ab - 4b ^ 2

= 81 - (9a ^ 2 + 12ab + 4b ^ 2)

 using (a + b) ^ 2 = a ^ 2 + 2ab + b ^ 2

= 81 - (3a + 2b) ^ 2

= 9 ^ 2 - (3a + 2b) ^ 2

= [9 - (3a + 2b)] [9 + (3a + 2b)]

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