x^2-21x-144=0

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Solution for x^2-21x-144=0 equation:


Simplifying
x2 + -21x + -144 = 0

Reorder the terms:
-144 + -21x + x2 = 0

Solving
-144 + -21x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '144' to each side of the equation.
-144 + -21x + 144 + x2 = 0 + 144

Reorder the terms:
-144 + 144 + -21x + x2 = 0 + 144

Combine like terms: -144 + 144 = 0
0 + -21x + x2 = 0 + 144
-21x + x2 = 0 + 144

Combine like terms: 0 + 144 = 144
-21x + x2 = 144

The x term is -21x.  Take half its coefficient (-10.5).
Square it (110.25) and add it to both sides.

Add '110.25' to each side of the equation.
-21x + 110.25 + x2 = 144 + 110.25

Reorder the terms:
110.25 + -21x + x2 = 144 + 110.25

Combine like terms: 144 + 110.25 = 254.25
110.25 + -21x + x2 = 254.25

Factor a perfect square on the left side:
(x + -10.5)(x + -10.5) = 254.25

Calculate the square root of the right side: 15.945218719

Break this problem into two subproblems by setting 
(x + -10.5) equal to 15.945218719 and -15.945218719.

Subproblem 1

x + -10.5 = 15.945218719 Simplifying x + -10.5 = 15.945218719 Reorder the terms: -10.5 + x = 15.945218719 Solving -10.5 + x = 15.945218719 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '10.5' to each side of the equation. -10.5 + 10.5 + x = 15.945218719 + 10.5 Combine like terms: -10.5 + 10.5 = 0.0 0.0 + x = 15.945218719 + 10.5 x = 15.945218719 + 10.5 Combine like terms: 15.945218719 + 10.5 = 26.445218719 x = 26.445218719 Simplifying x = 26.445218719

Subproblem 2

x + -10.5 = -15.945218719 Simplifying x + -10.5 = -15.945218719 Reorder the terms: -10.5 + x = -15.945218719 Solving -10.5 + x = -15.945218719 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '10.5' to each side of the equation. -10.5 + 10.5 + x = -15.945218719 + 10.5 Combine like terms: -10.5 + 10.5 = 0.0 0.0 + x = -15.945218719 + 10.5 x = -15.945218719 + 10.5 Combine like terms: -15.945218719 + 10.5 = -5.445218719 x = -5.445218719 Simplifying x = -5.445218719

Solution

The solution to the problem is based on the solutions from the subproblems. x = {26.445218719, -5.445218719}

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