x^2-7x-90=0

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Solution for x^2-7x-90=0 equation:


Simplifying
x2 + -7x + -90 = 0

Reorder the terms:
-90 + -7x + x2 = 0

Solving
-90 + -7x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '90' to each side of the equation.
-90 + -7x + 90 + x2 = 0 + 90

Reorder the terms:
-90 + 90 + -7x + x2 = 0 + 90

Combine like terms: -90 + 90 = 0
0 + -7x + x2 = 0 + 90
-7x + x2 = 0 + 90

Combine like terms: 0 + 90 = 90
-7x + x2 = 90

The x term is -7x.  Take half its coefficient (-3.5).
Square it (12.25) and add it to both sides.

Add '12.25' to each side of the equation.
-7x + 12.25 + x2 = 90 + 12.25

Reorder the terms:
12.25 + -7x + x2 = 90 + 12.25

Combine like terms: 90 + 12.25 = 102.25
12.25 + -7x + x2 = 102.25

Factor a perfect square on the left side:
(x + -3.5)(x + -3.5) = 102.25

Calculate the square root of the right side: 10.111874208

Break this problem into two subproblems by setting 
(x + -3.5) equal to 10.111874208 and -10.111874208.

Subproblem 1

x + -3.5 = 10.111874208 Simplifying x + -3.5 = 10.111874208 Reorder the terms: -3.5 + x = 10.111874208 Solving -3.5 + x = 10.111874208 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.5' to each side of the equation. -3.5 + 3.5 + x = 10.111874208 + 3.5 Combine like terms: -3.5 + 3.5 = 0.0 0.0 + x = 10.111874208 + 3.5 x = 10.111874208 + 3.5 Combine like terms: 10.111874208 + 3.5 = 13.611874208 x = 13.611874208 Simplifying x = 13.611874208

Subproblem 2

x + -3.5 = -10.111874208 Simplifying x + -3.5 = -10.111874208 Reorder the terms: -3.5 + x = -10.111874208 Solving -3.5 + x = -10.111874208 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.5' to each side of the equation. -3.5 + 3.5 + x = -10.111874208 + 3.5 Combine like terms: -3.5 + 3.5 = 0.0 0.0 + x = -10.111874208 + 3.5 x = -10.111874208 + 3.5 Combine like terms: -10.111874208 + 3.5 = -6.611874208 x = -6.611874208 Simplifying x = -6.611874208

Solution

The solution to the problem is based on the solutions from the subproblems. x = {13.611874208, -6.611874208}

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