Question

pls answer me .......

Answer 1

[(a-b)³ = a³ - b³ -3(ab)(a+b)]

Answer 2

(A-b) ^3=a^3-3ab(a-b)-b^3
here,
in (3r-2k)^3
3r=a and 2k=b
so, 27r^3-18rk(3r-2k)-8k^3 (ans)