Help me.

How to prove that:

1) 2cosa-cos3a-cos5a=16cos3a. sin2a

2) sina(cos2a+cos4a+cos6a)=cos4a. sin3a

Find the vertex of the function given below y=x^2-6x+1

Anyone know? will mark brainliest if you're correct!

Proceed as in example 3 in section 6.1 to rewrite the given expression using a single power series whose general term involves xk. ∞ n(n − 1)cnxn − 2 n = 2 − 4 ∞ ncnxn n = 1 + ∞ cnxn n = 0