What is the average of samples 8,7,6,9,12,8,10,12?

What is the average of samples 8,7,6,9,12,8,10,12?

(8 + 7 + 6 + 9 + 12 + 8 + 10 + 12) △ 8 = 9 Google calculator details

Prove with complex number: the sum of squares of parallelogram diagonal is equal to the sum of squares of four sides

Set four vertices, a = 0, B = x, C = x, C = m + min, d = (M-X) + in, B-A = x = C-D, C-B = (M-X) + in = D-A diagonal, C-A = m + min, D-B = (m-2x) (m-2x) + in there is |c-a|2 + |d-b-b|2 = M2 + N2 + m2-4mx + 4x2 + 4x2 + 4x2 + 4x2 + N2 = 2M2 + 2 + 2x2 + 2 + 2 + 2 + 2n2 + 2-2 + 2-2-2x2 + 2 + 2-4x2 + 2x2 + 2x2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2-2 + 2-2-2x2-4x2 + 2 + 2-4x2 + 2 + 2 + 2-4x2 + 2 + 2 + 2 + 2-4x2 + 2 + 2-2 2 + 2m

Prove with vector: the square sum of two diagonals of parallelogram is equal to the square sum of parallelogram?
Detailed explanation, symbols to let people know

Let AB = vector a, BC = vector B, then vector CD = vector - A, Da = vector - B, then vector AC = vector a + B, BD = vector B-A, vector AC & # 178; + vector BD & # 178; = vector A & # 178; + 2 vector a, vector B + vector B & # 178; + vector A & # 178; - 2 vector a vector B + vector B & # 17