x^2+40x-400=0

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Solution for x^2+40x-400=0 equation:


Simplifying
x2 + 40x + -400 = 0

Reorder the terms:
-400 + 40x + x2 = 0

Solving
-400 + 40x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '400' to each side of the equation.
-400 + 40x + 400 + x2 = 0 + 400

Reorder the terms:
-400 + 400 + 40x + x2 = 0 + 400

Combine like terms: -400 + 400 = 0
0 + 40x + x2 = 0 + 400
40x + x2 = 0 + 400

Combine like terms: 0 + 400 = 400
40x + x2 = 400

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 = 400 + 400

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

Combine like terms: 400 + 400 = 800
400 + 40x + x2 = 800

Factor a perfect square on the left side:
(x + 20)(x + 20) = 800

Calculate the square root of the right side: 28.284271247

Break this problem into two subproblems by setting 
(x + 20) equal to 28.284271247 and -28.284271247.

Subproblem 1

x + 20 = 28.284271247 Simplifying x + 20 = 28.284271247 Reorder the terms: 20 + x = 28.284271247 Solving 20 + x = 28.284271247 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 = 28.284271247 + -20 Combine like terms: 20 + -20 = 0 0 + x = 28.284271247 + -20 x = 28.284271247 + -20 Combine like terms: 28.284271247 + -20 = 8.284271247 x = 8.284271247 Simplifying x = 8.284271247

Subproblem 2

x + 20 = -28.284271247 Simplifying x + 20 = -28.284271247 Reorder the terms: 20 + x = -28.284271247 Solving 20 + x = -28.284271247 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 = -28.284271247 + -20 Combine like terms: 20 + -20 = 0 0 + x = -28.284271247 + -20 x = -28.284271247 + -20 Combine like terms: -28.284271247 + -20 = -48.284271247 x = -48.284271247 Simplifying x = -48.284271247

Solution

The solution to the problem is based on the solutions from the subproblems. x = {8.284271247, -48.284271247}

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