Expand this (2x + 7y)2

by

(i) (2x + 7y)2

(ii) (1/2 x + 2/3 y)2

Answer :

(i) (2x + 7y)2

It can be written as

= (2x)2 + 2 × 2x × 7y + (7y)2

So we get

= 4x2 + 28xy + 49y2

(ii) (1/2 x + 2/3 y)2

It can be written as

= (1/2 x)2 + 2 × ½x + 2/3y + (2/3 y)2

So we get

= ¼ x2 + 2/3 xy + 4/9 y2

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