x^2-x-78=0

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Solution for x^2-x-78=0 equation:


Simplifying
x2 + -1x + -78 = 0

Reorder the terms:
-78 + -1x + x2 = 0

Solving
-78 + -1x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '78' to each side of the equation.
-78 + -1x + 78 + x2 = 0 + 78

Reorder the terms:
-78 + 78 + -1x + x2 = 0 + 78

Combine like terms: -78 + 78 = 0
0 + -1x + x2 = 0 + 78
-1x + x2 = 0 + 78

Combine like terms: 0 + 78 = 78
-1x + x2 = 78

The x term is -1x.  Take half its coefficient (-0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
-1x + 0.25 + x2 = 78 + 0.25

Reorder the terms:
0.25 + -1x + x2 = 78 + 0.25

Combine like terms: 78 + 0.25 = 78.25
0.25 + -1x + x2 = 78.25

Factor a perfect square on the left side:
(x + -0.5)(x + -0.5) = 78.25

Calculate the square root of the right side: 8.845903006

Break this problem into two subproblems by setting 
(x + -0.5) equal to 8.845903006 and -8.845903006.

Subproblem 1

x + -0.5 = 8.845903006 Simplifying x + -0.5 = 8.845903006 Reorder the terms: -0.5 + x = 8.845903006 Solving -0.5 + x = 8.845903006 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.5' to each side of the equation. -0.5 + 0.5 + x = 8.845903006 + 0.5 Combine like terms: -0.5 + 0.5 = 0.0 0.0 + x = 8.845903006 + 0.5 x = 8.845903006 + 0.5 Combine like terms: 8.845903006 + 0.5 = 9.345903006 x = 9.345903006 Simplifying x = 9.345903006

Subproblem 2

x + -0.5 = -8.845903006 Simplifying x + -0.5 = -8.845903006 Reorder the terms: -0.5 + x = -8.845903006 Solving -0.5 + x = -8.845903006 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.5' to each side of the equation. -0.5 + 0.5 + x = -8.845903006 + 0.5 Combine like terms: -0.5 + 0.5 = 0.0 0.0 + x = -8.845903006 + 0.5 x = -8.845903006 + 0.5 Combine like terms: -8.845903006 + 0.5 = -8.345903006 x = -8.345903006 Simplifying x = -8.345903006

Solution

The solution to the problem is based on the solutions from the subproblems. x = {9.345903006, -8.345903006}

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