1.Let 9=x1<x2<⋯<x79 = x_1 < x_2 < \dots < x_79=x1<x2<⋯<x7 be in an A.P. with common difference ddd. If the standard deviation of x1,x2,…,x7x_1, x_2, \dots, x_7x1,x2,…,x7 is 444 and the mean is 151515, then x4+x6x_4 + x_6x4+x6 is equal to:a.18(1+d)18(1 + \sqrt{d})18(1+d)b.343434c.2(9+d)2(9 + \sqrt{d})2(9+d)d.252525Login to continueOnly logged in users canattempt or see the solution.
