Question

plz explan..this step

Answer 1

see let me explain u it's easy...
we can add and subtract the same thing so that it's value won't change...
same thing is done here..
juz add and subtract 3.a.1/a(a+1/a)..
the added part forms a formula for (a+1/a)^3

Answer 2

hence it can be written in the form of the formula.... hope it helps you..