0=X^2-X-7

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Solution for 0=X^2-X-7 equation:


Simplifying
0 = X2 + -1X + -7

Reorder the terms:
0 = -7 + -1X + X2

Solving
0 = -7 + -1X + X2

Solving for variable 'X'.

Combine like terms: 0 + 7 = 7
7 + X + -1X2 = -7 + -1X + X2 + 7 + X + -1X2

Reorder the terms:
7 + X + -1X2 = -7 + 7 + -1X + X + X2 + -1X2

Combine like terms: -7 + 7 = 0
7 + X + -1X2 = 0 + -1X + X + X2 + -1X2
7 + X + -1X2 = -1X + X + X2 + -1X2

Combine like terms: -1X + X = 0
7 + X + -1X2 = 0 + X2 + -1X2
7 + X + -1X2 = X2 + -1X2

Combine like terms: X2 + -1X2 = 0
7 + X + -1X2 = 0

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
-7 + -1X + X2 = 0

Move the constant term to the right:

Add '7' to each side of the equation.
-7 + -1X + 7 + X2 = 0 + 7

Reorder the terms:
-7 + 7 + -1X + X2 = 0 + 7

Combine like terms: -7 + 7 = 0
0 + -1X + X2 = 0 + 7
-1X + X2 = 0 + 7

Combine like terms: 0 + 7 = 7
-1X + X2 = 7

The X term is X.  Take half its coefficient (0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
-1X + 0.25 + X2 = 7 + 0.25

Reorder the terms:
0.25 + -1X + X2 = 7 + 0.25

Combine like terms: 7 + 0.25 = 7.25
0.25 + -1X + X2 = 7.25

Factor a perfect square on the left side:
(X + 0.5)(X + 0.5) = 7.25

Calculate the square root of the right side: 2.692582404

Break this problem into two subproblems by setting 
(X + 0.5) equal to 2.692582404 and -2.692582404.

Subproblem 1

X + 0.5 = 2.692582404 Simplifying X + 0.5 = 2.692582404 Reorder the terms: 0.5 + X = 2.692582404 Solving 0.5 + X = 2.692582404 Solving for variable 'X'. Move all terms containing X to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + X = 2.692582404 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + X = 2.692582404 + -0.5 X = 2.692582404 + -0.5 Combine like terms: 2.692582404 + -0.5 = 2.192582404 X = 2.192582404 Simplifying X = 2.192582404

Subproblem 2

X + 0.5 = -2.692582404 Simplifying X + 0.5 = -2.692582404 Reorder the terms: 0.5 + X = -2.692582404 Solving 0.5 + X = -2.692582404 Solving for variable 'X'. Move all terms containing X to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + X = -2.692582404 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + X = -2.692582404 + -0.5 X = -2.692582404 + -0.5 Combine like terms: -2.692582404 + -0.5 = -3.192582404 X = -3.192582404 Simplifying X = -3.192582404

Solution

The solution to the problem is based on the solutions from the subproblems. X = {2.192582404, -3.192582404}

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