Some Field Experience in the use of an Accelerated Method in Estimating 28-Day Strength of Concrete" considered regressing y =28-day standard-cured strength (psi) against x =accelerated strength (psi). Suppose the equation of the true regression line is y =1800 +1.3x.

a. What is the expected value of 28-day strength when accelerated strength= 2500? (2 marks)

b. By how much can we expect 28-day strength to change when accelerated strength increases by 1 psi? (4 marks)

c. Answer part (b) for an increase of 100 psi. (2 marks)

d. Answer part (b) for a decrease of 100 ps

Hello i need some with trigonometric substitutions. [tex]\int\limits^a_b {x} \, dx[/tex]

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

For what values of the variable x is the expression square root of 7x+14+ square root of 7-x a real number?