x(x-40)=80

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Solution for x(x-40)=80 equation:


Simplifying
x(x + -40) = 80

Reorder the terms:
x(-40 + x) = 80
(-40 * x + x * x) = 80
(-40x + x2) = 80

Solving
-40x + x2 = 80

Solving for variable 'x'.

Reorder the terms:
-80 + -40x + x2 = 80 + -80

Combine like terms: 80 + -80 = 0
-80 + -40x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '80' to each side of the equation.
-80 + -40x + 80 + x2 = 0 + 80

Reorder the terms:
-80 + 80 + -40x + x2 = 0 + 80

Combine like terms: -80 + 80 = 0
0 + -40x + x2 = 0 + 80
-40x + x2 = 0 + 80

Combine like terms: 0 + 80 = 80
-40x + x2 = 80

The x term is -40x.  Take half its coefficient (-20).
Square it (400) and add it to both sides.

Add '400' to each side of the equation.
-40x + 400 + x2 = 80 + 400

Reorder the terms:
400 + -40x + x2 = 80 + 400

Combine like terms: 80 + 400 = 480
400 + -40x + x2 = 480

Factor a perfect square on the left side:
(x + -20)(x + -20) = 480

Calculate the square root of the right side: 21.9089023

Break this problem into two subproblems by setting 
(x + -20) equal to 21.9089023 and -21.9089023.

Subproblem 1

x + -20 = 21.9089023 Simplifying x + -20 = 21.9089023 Reorder the terms: -20 + x = 21.9089023 Solving -20 + x = 21.9089023 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '20' to each side of the equation. -20 + 20 + x = 21.9089023 + 20 Combine like terms: -20 + 20 = 0 0 + x = 21.9089023 + 20 x = 21.9089023 + 20 Combine like terms: 21.9089023 + 20 = 41.9089023 x = 41.9089023 Simplifying x = 41.9089023

Subproblem 2

x + -20 = -21.9089023 Simplifying x + -20 = -21.9089023 Reorder the terms: -20 + x = -21.9089023 Solving -20 + x = -21.9089023 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '20' to each side of the equation. -20 + 20 + x = -21.9089023 + 20 Combine like terms: -20 + 20 = 0 0 + x = -21.9089023 + 20 x = -21.9089023 + 20 Combine like terms: -21.9089023 + 20 = -1.9089023 x = -1.9089023 Simplifying x = -1.9089023

Solution

The solution to the problem is based on the solutions from the subproblems. x = {41.9089023, -1.9089023}

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