Given,

⇒

Note: To solve the problems of limit similar to one in our question we use the formula mentioned below which can be derived using binomial theorem.

Formula to be used:

Using the formula we have –

3a^3–1 = 4(1)^4–1

⇒ 3a² = 4

⇒ a² = 4/3

∴ a = ± (2/√3)