Whole numbers greater than six but less than 16

Given f(t) = 282 - 53 +1, determine the function value f(2). do not include f(z) = in your answer

When you answer this can you explain

Is the product of two rational numbers irrational or rational? first, make a hypothesis by multiplying two rational numbers. then, use variables such as x=a/b and y=c/d and the closure property of integers to prove your hypothesis.