Power of a Real numbers with positive and negative exponent

Express as a power of a rational number with negative exponent. (((-3)/2)^(-2))^(-3)

Express as a power of a rational number with negative exponent. (2^(5)-:2^(8))xx2^(-7)

Fill in the blank spaces. [((-5)/(3))^(2)]^(5) can be expressed as a power of rational number with negative exponent as

Fill in the blanks. 2^(6)xx2^(-8) can be expressed as a power of rational number with positive exponent as ________.

negative integral exponent

What is meant by power of a lens ? When is it positive or negative? Define one dioptre.