Find the minimum value of (x−1)5(x−1)7+3(x−1)6+(x−1)5+1for x>1.
Solution — click to reveal
By AM-GM, (x−1)5(x−1)7+3(x−1)6+(x−1)5+1=(x−1)2+3(x−1)+1+(x−1)51=(x−1)2+(x−1)+(x−1)+(x−1)+1+(x−1)51≥66(x−1)2⋅(x−1)⋅(x−1)⋅(x−1)⋅1⋅(x−1)51=6.Equality occurs when x=2, so the minimum value is 6.