(X-1)(X-1)=21

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Solution for (X-1)(X-1)=21 equation:


Simplifying
(X + -1)(X + -1) = 21

Reorder the terms:
(-1 + X)(X + -1) = 21

Reorder the terms:
(-1 + X)(-1 + X) = 21

Multiply (-1 + X) * (-1 + X)
(-1(-1 + X) + X(-1 + X)) = 21
((-1 * -1 + X * -1) + X(-1 + X)) = 21
((1 + -1X) + X(-1 + X)) = 21
(1 + -1X + (-1 * X + X * X)) = 21
(1 + -1X + (-1X + X2)) = 21

Combine like terms: -1X + -1X = -2X
(1 + -2X + X2) = 21

Solving
1 + -2X + X2 = 21

Solving for variable 'X'.

Reorder the terms:
1 + -21 + -2X + X2 = 21 + -21

Combine like terms: 1 + -21 = -20
-20 + -2X + X2 = 21 + -21

Combine like terms: 21 + -21 = 0
-20 + -2X + X2 = 0

Begin completing the square.

Move the constant term to the right:

Add '20' to each side of the equation.
-20 + -2X + 20 + X2 = 0 + 20

Reorder the terms:
-20 + 20 + -2X + X2 = 0 + 20

Combine like terms: -20 + 20 = 0
0 + -2X + X2 = 0 + 20
-2X + X2 = 0 + 20

Combine like terms: 0 + 20 = 20
-2X + X2 = 20

The X term is -2X.  Take half its coefficient (-1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
-2X + 1 + X2 = 20 + 1

Reorder the terms:
1 + -2X + X2 = 20 + 1

Combine like terms: 20 + 1 = 21
1 + -2X + X2 = 21

Factor a perfect square on the left side:
(X + -1)(X + -1) = 21

Calculate the square root of the right side: 4.582575695

Break this problem into two subproblems by setting 
(X + -1) equal to 4.582575695 and -4.582575695.

Subproblem 1

X + -1 = 4.582575695 Simplifying X + -1 = 4.582575695 Reorder the terms: -1 + X = 4.582575695 Solving -1 + X = 4.582575695 Solving for variable 'X'. Move all terms containing X to the left, all other terms to the right. Add '1' to each side of the equation. -1 + 1 + X = 4.582575695 + 1 Combine like terms: -1 + 1 = 0 0 + X = 4.582575695 + 1 X = 4.582575695 + 1 Combine like terms: 4.582575695 + 1 = 5.582575695 X = 5.582575695 Simplifying X = 5.582575695

Subproblem 2

X + -1 = -4.582575695 Simplifying X + -1 = -4.582575695 Reorder the terms: -1 + X = -4.582575695 Solving -1 + X = -4.582575695 Solving for variable 'X'. Move all terms containing X to the left, all other terms to the right. Add '1' to each side of the equation. -1 + 1 + X = -4.582575695 + 1 Combine like terms: -1 + 1 = 0 0 + X = -4.582575695 + 1 X = -4.582575695 + 1 Combine like terms: -4.582575695 + 1 = -3.582575695 X = -3.582575695 Simplifying X = -3.582575695

Solution

The solution to the problem is based on the solutions from the subproblems. X = {5.582575695, -3.582575695}

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