X^2-21X+1=0

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Solution for X^2-21X+1=0 equation:


Simplifying
X2 + -21X + 1 = 0

Reorder the terms:
1 + -21X + X2 = 0

Solving
1 + -21X + X2 = 0

Solving for variable 'X'.

Begin completing the square.

Move the constant term to the right:

Add '-1' to each side of the equation.
1 + -21X + -1 + X2 = 0 + -1

Reorder the terms:
1 + -1 + -21X + X2 = 0 + -1

Combine like terms: 1 + -1 = 0
0 + -21X + X2 = 0 + -1
-21X + X2 = 0 + -1

Combine like terms: 0 + -1 = -1
-21X + X2 = -1

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 = -1 + 110.25

Reorder the terms:
110.25 + -21X + X2 = -1 + 110.25

Combine like terms: -1 + 110.25 = 109.25
110.25 + -21X + X2 = 109.25

Factor a perfect square on the left side:
(X + -10.5)(X + -10.5) = 109.25

Calculate the square root of the right side: 10.45227248

Break this problem into two subproblems by setting 
(X + -10.5) equal to 10.45227248 and -10.45227248.

Subproblem 1

X + -10.5 = 10.45227248 Simplifying X + -10.5 = 10.45227248 Reorder the terms: -10.5 + X = 10.45227248 Solving -10.5 + X = 10.45227248 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 = 10.45227248 + 10.5 Combine like terms: -10.5 + 10.5 = 0.0 0.0 + X = 10.45227248 + 10.5 X = 10.45227248 + 10.5 Combine like terms: 10.45227248 + 10.5 = 20.95227248 X = 20.95227248 Simplifying X = 20.95227248

Subproblem 2

X + -10.5 = -10.45227248 Simplifying X + -10.5 = -10.45227248 Reorder the terms: -10.5 + X = -10.45227248 Solving -10.5 + X = -10.45227248 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 = -10.45227248 + 10.5 Combine like terms: -10.5 + 10.5 = 0.0 0.0 + X = -10.45227248 + 10.5 X = -10.45227248 + 10.5 Combine like terms: -10.45227248 + 10.5 = 0.04772752 X = 0.04772752 Simplifying X = 0.04772752

Solution

The solution to the problem is based on the solutions from the subproblems. X = {20.95227248, 0.04772752}

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