(-X^2)+(12X)-21=0

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Solution for (-X^2)+(12X)-21=0 equation:


Simplifying
(-1X2) + (12X) + -21 = 0

Reorder the terms:
-21 + (12X) + (-1X2) = 0

Solving
-21 + (12X) + (-1X2) = 0

Solving for variable 'X'.

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

Divide each side by '-1'.
21 + (-12X) + X2 = 0

Move the constant term to the right:

Add '-21' to each side of the equation.
21 + (-12X) + -21 + X2 = 0 + -21

Reorder the terms:
21 + -21 + (-12X) + X2 = 0 + -21

Combine like terms: 21 + -21 = 0
0 + (-12X) + X2 = 0 + -21
(-12X) + X2 = 0 + -21

Combine like terms: 0 + -21 = -21
(-12X) + X2 = -21

The X term is (-12X).  Take half its coefficient (-6).
Square it (36) and add it to both sides.

Add '36' to each side of the equation.
(-12X) + 36 + X2 = -21 + 36

Reorder the terms:
36 + (-12X) + X2 = -21 + 36

Combine like terms: -21 + 36 = 15
36 + (-12X) + X2 = 15

Factor a perfect square on the left side:
((X) + -6)((X) + -6) = 15

Calculate the square root of the right side: 3.872983346

Break this problem into two subproblems by setting 
((X) + -6) equal to 3.872983346 and -3.872983346.

Subproblem 1

(X) + -6 = 3.872983346 Simplifying (X) + -6 = 3.872983346 X + -6 = 3.872983346 Reorder the terms: -6 + X = 3.872983346 Solving -6 + X = 3.872983346 Solving for variable 'X'. Move all terms containing X to the left, all other terms to the right. Add '6' to each side of the equation. -6 + 6 + X = 3.872983346 + 6 Combine like terms: -6 + 6 = 0 0 + X = 3.872983346 + 6 X = 3.872983346 + 6 Combine like terms: 3.872983346 + 6 = 9.872983346 X = 9.872983346 Simplifying X = 9.872983346

Subproblem 2

(X) + -6 = -3.872983346 Simplifying (X) + -6 = -3.872983346 X + -6 = -3.872983346 Reorder the terms: -6 + X = -3.872983346 Solving -6 + X = -3.872983346 Solving for variable 'X'. Move all terms containing X to the left, all other terms to the right. Add '6' to each side of the equation. -6 + 6 + X = -3.872983346 + 6 Combine like terms: -6 + 6 = 0 0 + X = -3.872983346 + 6 X = -3.872983346 + 6 Combine like terms: -3.872983346 + 6 = 2.127016654 X = 2.127016654 Simplifying X = 2.127016654

Solution

The solution to the problem is based on the solutions from the subproblems. X = {9.872983346, 2.127016654}

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