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Expansions — MATHEMATICS STD 9 — Question

ICSE BoardEnglish MediumSTD 9MATHEMATICSExpansions3 Marks
Question
Find the cube of: $4x + 7y$
✓

Answer

Using $(a + b)^3$
$= a^3 + b^3+ 3ab + (a + b)$
$(4x + 7y)^3$
$= (4x)^3+ (7y)^3 + 3(4x) (7y) (4x + 7y)$
$= 64x^3 + 343y^3 + 84xy (4x + 7y)$
$= 64x^3 + 343y^3 + 336x^2y + 588xy^2.$

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