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Expansions — MATHEMATICS STD 9 — Question

ICSE BoardEnglish MediumSTD 9MATHEMATICSExpansions3 Marks
Question
If $p - q = -1$ and $pq = -12,$ find $p^3 - q^3$
✓

Answer

$p - q = -1, pq = -12$
$(p - q)^3 = p^3- q^3 - 3pq (p - q)$
$\Rightarrow (-1)^3 = p^3 - q^3 - 3(-12) (-1)$
$\Rightarrow p^3 - q^3$
$= -14 + 36$
$= 35.$

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