x^2-14x=-21

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Solution for x^2-14x=-21 equation:


Simplifying
x2 + -14x = -21

Reorder the terms:
-14x + x2 = -21

Solving
-14x + x2 = -21

Solving for variable 'x'.

Reorder the terms:
21 + -14x + x2 = -21 + 21

Combine like terms: -21 + 21 = 0
21 + -14x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-21' to each side of the equation.
21 + -14x + -21 + x2 = 0 + -21

Reorder the terms:
21 + -21 + -14x + x2 = 0 + -21

Combine like terms: 21 + -21 = 0
0 + -14x + x2 = 0 + -21
-14x + x2 = 0 + -21

Combine like terms: 0 + -21 = -21
-14x + x2 = -21

The x term is -14x.  Take half its coefficient (-7).
Square it (49) and add it to both sides.

Add '49' to each side of the equation.
-14x + 49 + x2 = -21 + 49

Reorder the terms:
49 + -14x + x2 = -21 + 49

Combine like terms: -21 + 49 = 28
49 + -14x + x2 = 28

Factor a perfect square on the left side:
(x + -7)(x + -7) = 28

Calculate the square root of the right side: 5.291502622

Break this problem into two subproblems by setting 
(x + -7) equal to 5.291502622 and -5.291502622.

Subproblem 1

x + -7 = 5.291502622 Simplifying x + -7 = 5.291502622 Reorder the terms: -7 + x = 5.291502622 Solving -7 + x = 5.291502622 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '7' to each side of the equation. -7 + 7 + x = 5.291502622 + 7 Combine like terms: -7 + 7 = 0 0 + x = 5.291502622 + 7 x = 5.291502622 + 7 Combine like terms: 5.291502622 + 7 = 12.291502622 x = 12.291502622 Simplifying x = 12.291502622

Subproblem 2

x + -7 = -5.291502622 Simplifying x + -7 = -5.291502622 Reorder the terms: -7 + x = -5.291502622 Solving -7 + x = -5.291502622 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '7' to each side of the equation. -7 + 7 + x = -5.291502622 + 7 Combine like terms: -7 + 7 = 0 0 + x = -5.291502622 + 7 x = -5.291502622 + 7 Combine like terms: -5.291502622 + 7 = 1.708497378 x = 1.708497378 Simplifying x = 1.708497378

Solution

The solution to the problem is based on the solutions from the subproblems. x = {12.291502622, 1.708497378}

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