The square number is 19 less than 100, what is the number?

Apatient is given 50 mg dose of medicine the medicines effectiveness decreases every hour at a constant rate of 40% what is the exponential decay function that models this scenario how much medicine will be left in the patients system after 2 hours

How to choose the sign of the radical in the denominator of the formula for the distance from a point to a line.

Can any one me with the answers to these questions asap?