0=x^2-4x-7

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Solution for 0=x^2-4x-7 equation:


Simplifying
0 = x2 + -4x + -7

Reorder the terms:
0 = -7 + -4x + x2

Solving
0 = -7 + -4x + x2

Solving for variable 'x'.

Combine like terms: 0 + 7 = 7
7 + 4x + -1x2 = -7 + -4x + x2 + 7 + 4x + -1x2

Reorder the terms:
7 + 4x + -1x2 = -7 + 7 + -4x + 4x + x2 + -1x2

Combine like terms: -7 + 7 = 0
7 + 4x + -1x2 = 0 + -4x + 4x + x2 + -1x2
7 + 4x + -1x2 = -4x + 4x + x2 + -1x2

Combine like terms: -4x + 4x = 0
7 + 4x + -1x2 = 0 + x2 + -1x2
7 + 4x + -1x2 = x2 + -1x2

Combine like terms: x2 + -1x2 = 0
7 + 4x + -1x2 = 0

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

Divide each side by '-1'.
-7 + -4x + x2 = 0

Move the constant term to the right:

Add '7' to each side of the equation.
-7 + -4x + 7 + x2 = 0 + 7

Reorder the terms:
-7 + 7 + -4x + x2 = 0 + 7

Combine like terms: -7 + 7 = 0
0 + -4x + x2 = 0 + 7
-4x + x2 = 0 + 7

Combine like terms: 0 + 7 = 7
-4x + x2 = 7

The x term is -4x.  Take half its coefficient (-2).
Square it (4) and add it to both sides.

Add '4' to each side of the equation.
-4x + 4 + x2 = 7 + 4

Reorder the terms:
4 + -4x + x2 = 7 + 4

Combine like terms: 7 + 4 = 11
4 + -4x + x2 = 11

Factor a perfect square on the left side:
(x + -2)(x + -2) = 11

Calculate the square root of the right side: 3.31662479

Break this problem into two subproblems by setting 
(x + -2) equal to 3.31662479 and -3.31662479.

Subproblem 1

x + -2 = 3.31662479 Simplifying x + -2 = 3.31662479 Reorder the terms: -2 + x = 3.31662479 Solving -2 + x = 3.31662479 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + x = 3.31662479 + 2 Combine like terms: -2 + 2 = 0 0 + x = 3.31662479 + 2 x = 3.31662479 + 2 Combine like terms: 3.31662479 + 2 = 5.31662479 x = 5.31662479 Simplifying x = 5.31662479

Subproblem 2

x + -2 = -3.31662479 Simplifying x + -2 = -3.31662479 Reorder the terms: -2 + x = -3.31662479 Solving -2 + x = -3.31662479 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + x = -3.31662479 + 2 Combine like terms: -2 + 2 = 0 0 + x = -3.31662479 + 2 x = -3.31662479 + 2 Combine like terms: -3.31662479 + 2 = -1.31662479 x = -1.31662479 Simplifying x = -1.31662479

Solution

The solution to the problem is based on the solutions from the subproblems. x = {5.31662479, -1.31662479}

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