-81+25x^2-90x=0

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Solution for -81+25x^2-90x=0 equation:


Simplifying
-81 + 25x2 + -90x = 0

Reorder the terms:
-81 + -90x + 25x2 = 0

Solving
-81 + -90x + 25x2 = 0

Solving for variable 'x'.

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

Divide each side by '25'.
-3.24 + -3.6x + x2 = 0

Move the constant term to the right:

Add '3.24' to each side of the equation.
-3.24 + -3.6x + 3.24 + x2 = 0 + 3.24

Reorder the terms:
-3.24 + 3.24 + -3.6x + x2 = 0 + 3.24

Combine like terms: -3.24 + 3.24 = 0.00
0.00 + -3.6x + x2 = 0 + 3.24
-3.6x + x2 = 0 + 3.24

Combine like terms: 0 + 3.24 = 3.24
-3.6x + x2 = 3.24

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 = 3.24 + 3.24

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

Combine like terms: 3.24 + 3.24 = 6.48
3.24 + -3.6x + x2 = 6.48

Factor a perfect square on the left side:
(x + -1.8)(x + -1.8) = 6.48

Calculate the square root of the right side: 2.545584412

Break this problem into two subproblems by setting 
(x + -1.8) equal to 2.545584412 and -2.545584412.

Subproblem 1

x + -1.8 = 2.545584412 Simplifying x + -1.8 = 2.545584412 Reorder the terms: -1.8 + x = 2.545584412 Solving -1.8 + x = 2.545584412 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 = 2.545584412 + 1.8 Combine like terms: -1.8 + 1.8 = 0.0 0.0 + x = 2.545584412 + 1.8 x = 2.545584412 + 1.8 Combine like terms: 2.545584412 + 1.8 = 4.345584412 x = 4.345584412 Simplifying x = 4.345584412

Subproblem 2

x + -1.8 = -2.545584412 Simplifying x + -1.8 = -2.545584412 Reorder the terms: -1.8 + x = -2.545584412 Solving -1.8 + x = -2.545584412 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 = -2.545584412 + 1.8 Combine like terms: -1.8 + 1.8 = 0.0 0.0 + x = -2.545584412 + 1.8 x = -2.545584412 + 1.8 Combine like terms: -2.545584412 + 1.8 = -0.745584412 x = -0.745584412 Simplifying x = -0.745584412

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.345584412, -0.745584412}

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