Factorise each of the following:
$( i)$. $8a^{3}+b^{3}+12 a^{2} b+6 a b^{2}$
$( iii)$. $27-125 a^{3}-135a+225a^{2}$


Given: $( i)$. $8a^{3}+b^{3}+12 a^{2} b+6 a b^{2}$ $( ii)$. $27-125 a^{3}-135 a+225 a^{2}$

To do: To factorise the given polynomial.

Solution:

$( i).$ $8a^3 + b^3 + 12a^2b + 6ab^2$  

$= ( 2a)^3 + ( b)^3 + 3( 2a)( b)( 2a + b)$  

$= ( 2a + b)^3$                             [$\because a^3 + b^3 + 3ab( a + b) = ( a + b)^3$]


$( ii)$. $27-125a^3-135a+225a^2$

$=125a3-225a2+135a-27$

$=(5a)3+(-3)3+3(5a)(-3)(5a-3)$

$=( 5a-3)^3$                                [$\because a^3-b^3-3ab( a-b)=( a-b)^3$] 


Updated on: 10-Oct-2022

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