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Factorise :

(2a+b)3(a+2b)3(2a + b)^3 - (a + 2b)^3

Factorisation

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Answer

(2a+b)3(a+2b)3=[(2a+b)(a+2b)][(2a+b)2+(2a+b)×(a+2b)+(a+2b)2]=(2a+ba2b)[(2a)2+b2+4ab+2a×(a+2b)+b×(a+2b)+a2+(2b)2+4ab]=(ab)[4a2+b2+4ab+2a2+4ab+ab+2b2+a2+4b2+4ab]=(ab)(7a2+7b2+13ab)(2a + b)^3 - (a + 2b)^3\\[1em] = [(2a + b) - (a + 2b)][(2a + b)^2 + (2a + b) \times (a + 2b) + (a + 2b)^2]\\[1em] = (2a + b - a - 2b)[(2a)^2 + b^2 + 4ab + 2a \times (a + 2b) + b \times (a + 2b) + a^2 + (2b)^2 + 4ab]\\[1em] = (a - b)[4a^2 + b^2 + 4ab + 2a^2 + 4ab + ab + 2b^2 + a^2 + 4b^2 + 4ab]\\[1em] = (a - b)(7a^2 + 7b^2 + 13ab)

Hence,(2a+b)3(a+2b)3=(ab)(7a2+7b2+13ab)(2a + b)^3 - (a + 2b)^3 = (a - b)(7a^2 + 7b^2 + 13ab).

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