Let us prove

4

Let us prove

= 1

4

Let us prove

5

If x + z = 2y and b² = ac, then let us show that a^y–z b^z–x c^x–y = 1.

6

If a = xy^p–1, b = xy^q–1 and c = xy^r–1, then let us show that a^q–r b^r–p c^p–q = 1.