If 2^x.3^y.5^z = 2160, find the values of x, y and z. Hence, compute the value of 3^x.2^-y.5^-z.

If p = x^{m + n}.y^l, q = x^{n + l}.y^m and r = x^{l + m}.yⁿ, prove that

p^{m - n}.q^{n - l}.r^{l - m} = 1

If x = a^{m + n}, y = a^{n + l} and z = a^{l + m}, prove that x^myⁿz^l = xⁿy^lz^m.