D^2+2D-1=0

Solution for D^2+2D-1=0 equation:

Simplifying
D2 + 2D + -1 = 0

Reorder the terms:
-1 + 2D + D2 = 0

Solving
-1 + 2D + D2 = 0

Solving for variable 'D'.

Begin completing the square.

Move the constant term to the right:

Add '1' to each side of the equation.
-1 + 2D + 1 + D2 = 0 + 1

Reorder the terms:
-1 + 1 + 2D + D2 = 0 + 1

Combine like terms: -1 + 1 = 0
0 + 2D + D2 = 0 + 1
2D + D2 = 0 + 1

Combine like terms: 0 + 1 = 1
2D + D2 = 1

The D term is 2D.  Take half its coefficient (1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
2D + 1 + D2 = 1 + 1

Reorder the terms:
1 + 2D + D2 = 1 + 1

Combine like terms: 1 + 1 = 2
1 + 2D + D2 = 2

Factor a perfect square on the left side:
(D + 1)(D + 1) = 2

Calculate the square root of the right side: 1.414213562

Break this problem into two subproblems by setting 
(D + 1) equal to 1.414213562 and -1.414213562.

Subproblem 1
D + 1 = 1.414213562

Simplifying
D + 1 = 1.414213562

Reorder the terms:
1 + D = 1.414213562

Solving
1 + D = 1.414213562

Solving for variable 'D'.

Move all terms containing D to the left, all other terms to the right.

Add '-1' to each side of the equation.
1 + -1 + D = 1.414213562 + -1

Combine like terms: 1 + -1 = 0
0 + D = 1.414213562 + -1
D = 1.414213562 + -1

Combine like terms: 1.414213562 + -1 = 0.414213562
D = 0.414213562

Simplifying
D = 0.414213562

Subproblem 2
D + 1 = -1.414213562

Simplifying
D + 1 = -1.414213562

Reorder the terms:
1 + D = -1.414213562

Solving
1 + D = -1.414213562

Solving for variable 'D'.

Move all terms containing D to the left, all other terms to the right.

Add '-1' to each side of the equation.
1 + -1 + D = -1.414213562 + -1

Combine like terms: 1 + -1 = 0
0 + D = -1.414213562 + -1
D = -1.414213562 + -1

Combine like terms: -1.414213562 + -1 = -2.414213562
D = -2.414213562

Simplifying
D = -2.414213562

Solution
The solution to the problem is based on the solutions
from the subproblems.
D = {0.414213562, -2.414213562}