Tracy has a cell phone plan that provides 250 free minutes each month for a flat rate of $29. for any minutes over 250, tracy is charged $0.35 per minute. which of the following piecewise functions represents charges based on tracy's cell phone plan?

The rate of decay of a radioactive substance depends upon the amount present initially. the mass y (mg) of the radioactive substance cobalt-60 present in a sample at time t (years) is represented by the exponential equation y=50e −0.1315 t . answer the following questions in complete sentences. 1. how does the exponential equation above compare to the equation for simple interest that is compounded continuously? explain the similarities. 2. what is the initial amount of cobalt-60 in the sample? 2. how much cobalt-60 is left after 8.4 years? show your work. 3. what would be the y-intercept of the graph? what does it represent? 4. after how many years will the amount of cobalt-60 left be 6.25 mg? explain what happens to the cobalt-60 after 50 years? 5. discuss some “real-world” examples and uses of cobalt-60

The radius of the earth is two times the radius of the moon. what fraction of the volume of the earth is the volume of the moon?

Which expression do you get when you eliminate the negative exponents of 4a^2 b^216a^-3 b