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Identities — MATHS STD 8 — Question

ICSE BoardEnglish MediumSTD 8MATHSIdentities4 Marks
Question
Evaluate : $(2a +3) (2a − 3) (4a^2 + 9)$
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Answer

$(2a +3) (2a − 3) (4a^2 + 9)$
$= [(2a)^2 − (3)^2] (4a^2 + 9) ..........[(a+b) (a−b) = a^2 − b^2]$
$= (4a^2 − 9) (4a^2 + 9)$
$= (4a^2)^2 − (9)^2 .........[(a+b) (a−b) = a^2 − b^2]$
$= 16a^4 − 81$

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