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Mathematics

(x + y)2 - 3(x + y) - 4 is equal to :

  1. (x + y + 4) (x + y - 1)

  2. (x + y + 4) (x + y + 1)

  3. (x + y - 4) (x + y + 1)

  4. (x + y - 4) (x + y - 1)

Factorisation

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Answer

(x + y)2 - 3(x + y) - 4

= (x + y)2 + (- 4 + 1)(x + y) - 4

= (x + y)2 + (- 4 + 1)(x + y) - 4

= (x + y)2 - 4(x + y) + 1(x + y) - 4

= [(x + y)2 - 4(x + y)] + [1(x + y) + 4]

= (x + y)[(x + y) - 4] + 1[(x + y) + 4]

= [(x + y) + 1][(x + y) - 4]

= [x + y + 1][x + y - 4]

Hence, option 3 is the correct option.

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