## College Algebra (6th Edition)

Given k = 1 to 4 then the sum = (1 - 3)(1 + 2) + (2 - 3)(2 + 2) + (3 - 3)(3 + 2) + (4 - 3)(4 + 2) = (-2)$\times$3 + (-1)$\times$4 + 0$\times$5 + 1$\times$6 = - 6 - 4 + 0 + 6 = -4