Question
Find the cube of : $3a- 2b$
✓
Answer
$( a - b )^3 = a^3 - 3ab( a - b ) - b^3$
$( 3a - 2b )^3 = (3a)^3 - 3 \times 3a \times 2b( 3a - 2b) - (2b)^3$
$= 27a^3 - 18ab( 3a - 2b ) - 8b^3$
$= 27a^3 - 54a^2b + 36ab^2 - 8b^3$
$( 3a - 2b )^3 = (3a)^3 - 3 \times 3a \times 2b( 3a - 2b) - (2b)^3$
$= 27a^3 - 18ab( 3a - 2b ) - 8b^3$
$= 27a^3 - 54a^2b + 36ab^2 - 8b^3$
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