(i) (3x + 1/x)3
(ii) (2x – 1)3
Answer :
(i) (3x + 1/x)3
It can be written as
= (3x)3 + (1/x)3 + 3 × 3x × 1/x (3x + 1/x)
By further calculation
= 27x3 + 1/x3 + 9 (3x + 1/x)
So we get
= 27x3 + 1/x3 + 27x + 9/x
(ii) (2x – 1)3
It can be written as
= (2x)3 – 13 – 3 × 2x × 1 (2x – 1)
By further calculation
= 8x3 – 1 – 6x (2x – 1)
So we get
= 8x3 – 1 – 12x2 + 6x
= 8x3 – 12x2 + 6x – 1
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