5x^2-18x-90=0

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Solution for 5x^2-18x-90=0 equation:


Simplifying
5x2 + -18x + -90 = 0

Reorder the terms:
-90 + -18x + 5x2 = 0

Solving
-90 + -18x + 5x2 = 0

Solving for variable 'x'.

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

Divide each side by '5'.
-18 + -3.6x + x2 = 0

Move the constant term to the right:

Add '18' to each side of the equation.
-18 + -3.6x + 18 + x2 = 0 + 18

Reorder the terms:
-18 + 18 + -3.6x + x2 = 0 + 18

Combine like terms: -18 + 18 = 0
0 + -3.6x + x2 = 0 + 18
-3.6x + x2 = 0 + 18

Combine like terms: 0 + 18 = 18
-3.6x + x2 = 18

The x term is -3.6x.  Take half its coefficient (-1.8).
Square it (3.24) and add it to both sides.

Add '3.24' to each side of the equation.
-3.6x + 3.24 + x2 = 18 + 3.24

Reorder the terms:
3.24 + -3.6x + x2 = 18 + 3.24

Combine like terms: 18 + 3.24 = 21.24
3.24 + -3.6x + x2 = 21.24

Factor a perfect square on the left side:
(x + -1.8)(x + -1.8) = 21.24

Calculate the square root of the right side: 4.608687449

Break this problem into two subproblems by setting 
(x + -1.8) equal to 4.608687449 and -4.608687449.

Subproblem 1

x + -1.8 = 4.608687449 Simplifying x + -1.8 = 4.608687449 Reorder the terms: -1.8 + x = 4.608687449 Solving -1.8 + x = 4.608687449 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.8' to each side of the equation. -1.8 + 1.8 + x = 4.608687449 + 1.8 Combine like terms: -1.8 + 1.8 = 0.0 0.0 + x = 4.608687449 + 1.8 x = 4.608687449 + 1.8 Combine like terms: 4.608687449 + 1.8 = 6.408687449 x = 6.408687449 Simplifying x = 6.408687449

Subproblem 2

x + -1.8 = -4.608687449 Simplifying x + -1.8 = -4.608687449 Reorder the terms: -1.8 + x = -4.608687449 Solving -1.8 + x = -4.608687449 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.8' to each side of the equation. -1.8 + 1.8 + x = -4.608687449 + 1.8 Combine like terms: -1.8 + 1.8 = 0.0 0.0 + x = -4.608687449 + 1.8 x = -4.608687449 + 1.8 Combine like terms: -4.608687449 + 1.8 = -2.808687449 x = -2.808687449 Simplifying x = -2.808687449

Solution

The solution to the problem is based on the solutions from the subproblems. x = {6.408687449, -2.808687449}

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