0=x^2-7x-20

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Solution for 0=x^2-7x-20 equation:


Simplifying
0 = x2 + -7x + -20

Reorder the terms:
0 = -20 + -7x + x2

Solving
0 = -20 + -7x + x2

Solving for variable 'x'.

Combine like terms: 0 + 20 = 20
20 + 7x + -1x2 = -20 + -7x + x2 + 20 + 7x + -1x2

Reorder the terms:
20 + 7x + -1x2 = -20 + 20 + -7x + 7x + x2 + -1x2

Combine like terms: -20 + 20 = 0
20 + 7x + -1x2 = 0 + -7x + 7x + x2 + -1x2
20 + 7x + -1x2 = -7x + 7x + x2 + -1x2

Combine like terms: -7x + 7x = 0
20 + 7x + -1x2 = 0 + x2 + -1x2
20 + 7x + -1x2 = x2 + -1x2

Combine like terms: x2 + -1x2 = 0
20 + 7x + -1x2 = 0

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

Divide each side by '-1'.
-20 + -7x + x2 = 0

Move the constant term to the right:

Add '20' to each side of the equation.
-20 + -7x + 20 + x2 = 0 + 20

Reorder the terms:
-20 + 20 + -7x + x2 = 0 + 20

Combine like terms: -20 + 20 = 0
0 + -7x + x2 = 0 + 20
-7x + x2 = 0 + 20

Combine like terms: 0 + 20 = 20
-7x + x2 = 20

The x term is -7x.  Take half its coefficient (-3.5).
Square it (12.25) and add it to both sides.

Add '12.25' to each side of the equation.
-7x + 12.25 + x2 = 20 + 12.25

Reorder the terms:
12.25 + -7x + x2 = 20 + 12.25

Combine like terms: 20 + 12.25 = 32.25
12.25 + -7x + x2 = 32.25

Factor a perfect square on the left side:
(x + -3.5)(x + -3.5) = 32.25

Calculate the square root of the right side: 5.678908346

Break this problem into two subproblems by setting 
(x + -3.5) equal to 5.678908346 and -5.678908346.

Subproblem 1

x + -3.5 = 5.678908346 Simplifying x + -3.5 = 5.678908346 Reorder the terms: -3.5 + x = 5.678908346 Solving -3.5 + x = 5.678908346 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.5' to each side of the equation. -3.5 + 3.5 + x = 5.678908346 + 3.5 Combine like terms: -3.5 + 3.5 = 0.0 0.0 + x = 5.678908346 + 3.5 x = 5.678908346 + 3.5 Combine like terms: 5.678908346 + 3.5 = 9.178908346 x = 9.178908346 Simplifying x = 9.178908346

Subproblem 2

x + -3.5 = -5.678908346 Simplifying x + -3.5 = -5.678908346 Reorder the terms: -3.5 + x = -5.678908346 Solving -3.5 + x = -5.678908346 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.5' to each side of the equation. -3.5 + 3.5 + x = -5.678908346 + 3.5 Combine like terms: -3.5 + 3.5 = 0.0 0.0 + x = -5.678908346 + 3.5 x = -5.678908346 + 3.5 Combine like terms: -5.678908346 + 3.5 = -2.178908346 x = -2.178908346 Simplifying x = -2.178908346

Solution

The solution to the problem is based on the solutions from the subproblems. x = {9.178908346, -2.178908346}

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