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Identities — MATHS STD 8 — Question

ICSE BoardEnglish MediumSTD 8MATHSIdentities4 Marks
Question
Find the square of $3a − 2b − 5c$
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Answer

$(3a − 2b − 5c)^2 $
$= (3a)^2 + (−2b)^2+ (−5c)^2 + 2 \times 3a \times −2b + 2 \times (−2b)(−5c) + 2 \times −5c \times 3a$
$= 9a^2 + 4b^2 + 25c^2− 12ab + 20bc − 30ca$

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