The sum of the first n terms of an arithmetic sequence is n/2(4n+20)

a) Write down the expression for the sum of the first

(n-1)

terms. [3 marks]

b) Find the first term and the common difference of the above sequence.

When can a theory be modified if a new type of technology allows for new observations that raise new questions? a-immediately, while the questions about the theory are being asked b-after new hypotheses related to the theory are tested in experiments c-only after the new observations disprove all parts of the theory d-while scientists begin to think about how the theory could improve