First simplify, then evaluate: (2A / A-1 + A / 1-A) △ a, where √ 2 + 1 asks for the help of the great God

First simplify, then evaluate: (2A / A-1 + A / 1-A) △ a, where √ 2 + 1 asks for the help of the great God

After simplification, 1 / (A-1) is evaluated as: the root of two

First simplify and then evaluate: [4 (a + b) (a-b) - (2a-b)] + 3AB, where a = 1 / 2,

[4 (a + b) (a-b) - (2a-b)] + 3AB = 4 (a-b) - (4a + b-4ab) + 3AB = 4a-4b-4a-b + 4AB + 3AB = - 5B + 7ab because a = 1 / 2, B = 3, so the original formula = - 5x9 + 7X3 / 2 = 21 / 2-45 = - 69 / 2

1 + (1 + 2) + (1 + 2 + 3) + (1 + 2 + 3 + 4) +. + (1 + 2 + 3 + 4 +. + n) simplify the great gods to help

First, 1 + 2 + 3 +. + n = 0.5N (n + 1) ｜ 1 + (1 + 2) + (1 + 2 + 3) +. + (1 + 2 + 3 +.. + n) = 0.5 [(1 ^ 2 + 1) + (2 ^ 2 + 2) +... (n ^ 2 + n)] = 0.5 [1 ^ 2 +... + n ^ 2] + 0.5 [1 + 2 +... + n] = [n (n + 1) (2n-1) / 12] + [n (n + 1) / 4] and click "can solve + original"!