Expand (x + 2)3

(i) (x + 2)3

(ii) (2a + b)3

Answer :

(i) (x + 2)3

It can be written as

= x3 + 23 + 3 × x × 2 (x + 2)

By further calculation

= x3 + 8 + 6x (x + 2)

So we get

= x3 + 8 + 6x2 + 12x

= x3 + 6x2 + 12x + 8

(ii) (2a + b)3

It can be written as

= (2a)3 + b3 + 3 × 2a × b (2a + b)

By further calculation

= 8a3 + b3 + 6ab (2a + b)

So we get

= 8a3 + b3 + 12a2b + 6ab2

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