x^2+7x=42

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Solution for x^2+7x=42 equation:


Simplifying
x2 + 7x = 42

Reorder the terms:
7x + x2 = 42

Solving
7x + x2 = 42

Solving for variable 'x'.

Reorder the terms:
-42 + 7x + x2 = 42 + -42

Combine like terms: 42 + -42 = 0
-42 + 7x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '42' to each side of the equation.
-42 + 7x + 42 + x2 = 0 + 42

Reorder the terms:
-42 + 42 + 7x + x2 = 0 + 42

Combine like terms: -42 + 42 = 0
0 + 7x + x2 = 0 + 42
7x + x2 = 0 + 42

Combine like terms: 0 + 42 = 42
7x + x2 = 42

The x term is 7x.  Take half its coefficient (3.5).
Square it (12.25) and add it to both sides.

Add '12.25' to each side of the equation.
7x + 12.25 + x2 = 42 + 12.25

Reorder the terms:
12.25 + 7x + x2 = 42 + 12.25

Combine like terms: 42 + 12.25 = 54.25
12.25 + 7x + x2 = 54.25

Factor a perfect square on the left side:
(x + 3.5)(x + 3.5) = 54.25

Calculate the square root of the right side: 7.365459931

Break this problem into two subproblems by setting 
(x + 3.5) equal to 7.365459931 and -7.365459931.

Subproblem 1

x + 3.5 = 7.365459931 Simplifying x + 3.5 = 7.365459931 Reorder the terms: 3.5 + x = 7.365459931 Solving 3.5 + x = 7.365459931 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.5' to each side of the equation. 3.5 + -3.5 + x = 7.365459931 + -3.5 Combine like terms: 3.5 + -3.5 = 0.0 0.0 + x = 7.365459931 + -3.5 x = 7.365459931 + -3.5 Combine like terms: 7.365459931 + -3.5 = 3.865459931 x = 3.865459931 Simplifying x = 3.865459931

Subproblem 2

x + 3.5 = -7.365459931 Simplifying x + 3.5 = -7.365459931 Reorder the terms: 3.5 + x = -7.365459931 Solving 3.5 + x = -7.365459931 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.5' to each side of the equation. 3.5 + -3.5 + x = -7.365459931 + -3.5 Combine like terms: 3.5 + -3.5 = 0.0 0.0 + x = -7.365459931 + -3.5 x = -7.365459931 + -3.5 Combine like terms: -7.365459931 + -3.5 = -10.865459931 x = -10.865459931 Simplifying x = -10.865459931

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.865459931, -10.865459931}

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