Question

Listen here, the que given is ,if we expand (999)cube the answer will be n t options given are a)1124864 b)1214864 c)2124564 d)1142864 help me out plzzz

Answer 1

a^3 + b^3 = (a + b) × (a^2 – ab + b^2) ⇔ a^3 = (a + b) × (a^2 – ab + b^2) – b^3

With a = 999, b = 998 and the equivalence we get:

999^3 = 1997 x (999^2 – 999 × 998 + 998^2) – 998^3 = 1997 x (998001 – 997002 + 996004) – 994011992 = 1997 x 997003 – 994011992 = 997002999