#7. Observe that for n := k(k + 1)/2, a triangular number, we have 8n?42 = 8(k(k+1)/2)>+2 = 2(k(k+1)2+2 = 2((k(k+1))2+1). Then, since 2 = 12 + 12, the last line above can be written as a sum of two squares. 7. (10 points)Let n = k(k + 1)/2 (k > 1) be a triangular number. Prove that 8n* + 2 is written as sum of two squares