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Which expression is equivalent to (3^2)^-2 a.-81 b.-12 c.1/81 d.1/12

Asocial networking site currently has 400,000 active members, and that figure is predicted to increase by 32% each year. the following expression represents the number of active members on the site after t years.

One integer is 8 times another. if the product is 72, then find the integers