How can the right equation be converted into the answer on the left?

Question

(sec^4x)(tan^2x)=(tan^2x + tan^4x)sec^2x

Answer 1

RS = tan^2x(1 + tan^2x)(sec^2x)
= tan^2x(sec^2x)(sec^2x) , because 1 + tan^2x = sec^2x
= tan^2x(sec^4x)
= LS