Question

a^3+3a^2+9a=1 then a^3+3/a=?

Answer 1

Given that

a³+3a²+9a = 1           ...(1)

a(a²+3a+9) = 1

So 1/a = a²+3a+9

⇒ 3/a = 3a²+9a+27       ...(2)

Hence value of

a³+3/a = a³+3a²+9a+27         [ using (1) ]

a³+3/a = 1+27                         [ using (2) ]

a³+3/a = 28