Slader In this problem we want to calculate the number of two element lists (a, b) we can form using the numbers 0, 1, . . . n with a < b. (a) Show that the answer is (n + 1)n/2 by considering the number of two-element lists (a, b) in which a < b or a > b. (b) Show that the answer is also 1 + 2 + 3 + · · · + n. Taken together (a) and (b) prove the formula Xn k=1 k = (n + 1)n 2

Me! i'm really confused the isosceles trapezoids, abcd and efgh, are similar quadrilaterals. the scale factor between the trapezoids is 2: 3, line gh = 6 centimeters, line ad = 8 centimeters, and line ab is three times the length of line dc . use complete sentences to answer the following prompts and include all of your calculations in your final answer. a. write a similarity statement for each of the four pair of corresponding sides. b. write a congruence statement for each of the four pair of corresponding angles. c. determine the perimeter for each of the isosceles trapezoids.