25x^2-40x+9=81

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Solution for 25x^2-40x+9=81 equation:


Simplifying
25x2 + -40x + 9 = 81

Reorder the terms:
9 + -40x + 25x2 = 81

Solving
9 + -40x + 25x2 = 81

Solving for variable 'x'.

Reorder the terms:
9 + -81 + -40x + 25x2 = 81 + -81

Combine like terms: 9 + -81 = -72
-72 + -40x + 25x2 = 81 + -81

Combine like terms: 81 + -81 = 0
-72 + -40x + 25x2 = 0

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

Divide each side by '25'.
-2.88 + -1.6x + x2 = 0

Move the constant term to the right:

Add '2.88' to each side of the equation.
-2.88 + -1.6x + 2.88 + x2 = 0 + 2.88

Reorder the terms:
-2.88 + 2.88 + -1.6x + x2 = 0 + 2.88

Combine like terms: -2.88 + 2.88 = 0.00
0.00 + -1.6x + x2 = 0 + 2.88
-1.6x + x2 = 0 + 2.88

Combine like terms: 0 + 2.88 = 2.88
-1.6x + x2 = 2.88

The x term is -1.6x.  Take half its coefficient (-0.8).
Square it (0.64) and add it to both sides.

Add '0.64' to each side of the equation.
-1.6x + 0.64 + x2 = 2.88 + 0.64

Reorder the terms:
0.64 + -1.6x + x2 = 2.88 + 0.64

Combine like terms: 2.88 + 0.64 = 3.52
0.64 + -1.6x + x2 = 3.52

Factor a perfect square on the left side:
(x + -0.8)(x + -0.8) = 3.52

Calculate the square root of the right side: 1.876166304

Break this problem into two subproblems by setting 
(x + -0.8) equal to 1.876166304 and -1.876166304.

Subproblem 1

x + -0.8 = 1.876166304 Simplifying x + -0.8 = 1.876166304 Reorder the terms: -0.8 + x = 1.876166304 Solving -0.8 + x = 1.876166304 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.8' to each side of the equation. -0.8 + 0.8 + x = 1.876166304 + 0.8 Combine like terms: -0.8 + 0.8 = 0.0 0.0 + x = 1.876166304 + 0.8 x = 1.876166304 + 0.8 Combine like terms: 1.876166304 + 0.8 = 2.676166304 x = 2.676166304 Simplifying x = 2.676166304

Subproblem 2

x + -0.8 = -1.876166304 Simplifying x + -0.8 = -1.876166304 Reorder the terms: -0.8 + x = -1.876166304 Solving -0.8 + x = -1.876166304 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.8' to each side of the equation. -0.8 + 0.8 + x = -1.876166304 + 0.8 Combine like terms: -0.8 + 0.8 = 0.0 0.0 + x = -1.876166304 + 0.8 x = -1.876166304 + 0.8 Combine like terms: -1.876166304 + 0.8 = -1.076166304 x = -1.076166304 Simplifying x = -1.076166304

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.676166304, -1.076166304}

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