Expected value?

Question

higher mathematics

We need to find a mat. expectation according to this formula. Where did (16-1) come from at the end and why did x^2 become x^4?

Answer 1

Where did it come from at the end (16-1)

See definite integral and Newton-Leibniz formula .

why did x^2 become x^4?

See the list of integrals of elementary functions .