x*x+(x+9)=90

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Solution for x*x+(x+9)=90 equation:


Simplifying
x * x + (x + 9) = 90

Multiply x * x
x2 + (x + 9) = 90

Reorder the terms:
x2 + (9 + x) = 90

Remove parenthesis around (9 + x)
x2 + 9 + x = 90

Reorder the terms:
9 + x + x2 = 90

Solving
9 + x + x2 = 90

Solving for variable 'x'.

Reorder the terms:
9 + -90 + x + x2 = 90 + -90

Combine like terms: 9 + -90 = -81
-81 + x + x2 = 90 + -90

Combine like terms: 90 + -90 = 0
-81 + x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '81' to each side of the equation.
-81 + x + 81 + x2 = 0 + 81

Reorder the terms:
-81 + 81 + x + x2 = 0 + 81

Combine like terms: -81 + 81 = 0
0 + x + x2 = 0 + 81
x + x2 = 0 + 81

Combine like terms: 0 + 81 = 81
x + x2 = 81

The x term is x.  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.
x + 0.25 + x2 = 81 + 0.25

Reorder the terms:
0.25 + x + x2 = 81 + 0.25

Combine like terms: 81 + 0.25 = 81.25
0.25 + x + x2 = 81.25

Factor a perfect square on the left side:
(x + 0.5)(x + 0.5) = 81.25

Calculate the square root of the right side: 9.013878189

Break this problem into two subproblems by setting 
(x + 0.5) equal to 9.013878189 and -9.013878189.

Subproblem 1

x + 0.5 = 9.013878189 Simplifying x + 0.5 = 9.013878189 Reorder the terms: 0.5 + x = 9.013878189 Solving 0.5 + x = 9.013878189 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 = 9.013878189 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + x = 9.013878189 + -0.5 x = 9.013878189 + -0.5 Combine like terms: 9.013878189 + -0.5 = 8.513878189 x = 8.513878189 Simplifying x = 8.513878189

Subproblem 2

x + 0.5 = -9.013878189 Simplifying x + 0.5 = -9.013878189 Reorder the terms: 0.5 + x = -9.013878189 Solving 0.5 + x = -9.013878189 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 = -9.013878189 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + x = -9.013878189 + -0.5 x = -9.013878189 + -0.5 Combine like terms: -9.013878189 + -0.5 = -9.513878189 x = -9.513878189 Simplifying x = -9.513878189

Solution

The solution to the problem is based on the solutions from the subproblems. x = {8.513878189, -9.513878189}

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