Someone tell me how to do this

Write a numerical expression that satisfies all of the following conditions. 1.)the only number used in the expression is 5 2.)at least one exponent other than 1 is used 3.)when the expression is evaluated, the answer is greater than 40 and less than 50

The depth of a lake at a certain point, wich is a function of the distance of that point from shore, is 30 feet.

What signals you that factoring by grouping is the best method to use when factoring a problem?