i) 27(m3−8n3)
...[Taking out the common factor 27]
=27[m3−(2n)3]
Here, a = m and b = 2n
∴27m3−216n3
=27{(m−2n)[m2+m(2n)+(2n)2]}
....[∵a3−b3=(a−b)(a2+ab+b2)]
=27(m−2n)(m2+2mn+4n2)
ii) 343a3−512b3
=(7a)3−(8b)3
Here, A = 7a and B = 8b
∴343a3−512b3
=(7a−8b)[(7a)2+(7a)(8b)+(8b)2]
...[∵a3−b3=(a−b)(a2+ab+b2)]
=(7a−8b)(49a2+56ab+64b2