Givearecursivedefi of positive integers. [ hint: plot the points in the setin the plane and look for lines containing points in theset.] a) s = { (a, b) | a ∈ z + ,b ∈ z + , and a + b is odd } b) s = { (a, b) | a ∈ z + ,b ∈ z + , and a | b } c) s = { (a, b) | a ∈ z + ,b ∈ z + , and 3 | a + b slader

Use the radius you found in part i (r=26.8 cm) with the surface area formula below to find the surface area of the sphere. show your work and round your answer to the nearest tenth. the surface area of a sphere: sa = 4πr^2 self note: 3.8.4

Classify the following triangle check all that apply

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