b^2-12b-42=0

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Solution for b^2-12b-42=0 equation:


Simplifying
b2 + -12b + -42 = 0

Reorder the terms:
-42 + -12b + b2 = 0

Solving
-42 + -12b + b2 = 0

Solving for variable 'b'.

Begin completing the square.

Move the constant term to the right:

Add '42' to each side of the equation.
-42 + -12b + 42 + b2 = 0 + 42

Reorder the terms:
-42 + 42 + -12b + b2 = 0 + 42

Combine like terms: -42 + 42 = 0
0 + -12b + b2 = 0 + 42
-12b + b2 = 0 + 42

Combine like terms: 0 + 42 = 42
-12b + b2 = 42

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

Add '36' to each side of the equation.
-12b + 36 + b2 = 42 + 36

Reorder the terms:
36 + -12b + b2 = 42 + 36

Combine like terms: 42 + 36 = 78
36 + -12b + b2 = 78

Factor a perfect square on the left side:
(b + -6)(b + -6) = 78

Calculate the square root of the right side: 8.831760866

Break this problem into two subproblems by setting 
(b + -6) equal to 8.831760866 and -8.831760866.

Subproblem 1

b + -6 = 8.831760866 Simplifying b + -6 = 8.831760866 Reorder the terms: -6 + b = 8.831760866 Solving -6 + b = 8.831760866 Solving for variable 'b'. Move all terms containing b to the left, all other terms to the right. Add '6' to each side of the equation. -6 + 6 + b = 8.831760866 + 6 Combine like terms: -6 + 6 = 0 0 + b = 8.831760866 + 6 b = 8.831760866 + 6 Combine like terms: 8.831760866 + 6 = 14.831760866 b = 14.831760866 Simplifying b = 14.831760866

Subproblem 2

b + -6 = -8.831760866 Simplifying b + -6 = -8.831760866 Reorder the terms: -6 + b = -8.831760866 Solving -6 + b = -8.831760866 Solving for variable 'b'. Move all terms containing b to the left, all other terms to the right. Add '6' to each side of the equation. -6 + 6 + b = -8.831760866 + 6 Combine like terms: -6 + 6 = 0 0 + b = -8.831760866 + 6 b = -8.831760866 + 6 Combine like terms: -8.831760866 + 6 = -2.831760866 b = -2.831760866 Simplifying b = -2.831760866

Solution

The solution to the problem is based on the solutions from the subproblems. b = {14.831760866, -2.831760866}

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