3x^2+21x+36=4

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Solution for 3x^2+21x+36=4 equation:


Simplifying
3x2 + 21x + 36 = 4

Reorder the terms:
36 + 21x + 3x2 = 4

Solving
36 + 21x + 3x2 = 4

Solving for variable 'x'.

Reorder the terms:
36 + -4 + 21x + 3x2 = 4 + -4

Combine like terms: 36 + -4 = 32
32 + 21x + 3x2 = 4 + -4

Combine like terms: 4 + -4 = 0
32 + 21x + 3x2 = 0

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

Divide each side by '3'.
10.66666667 + 7x + x2 = 0

Move the constant term to the right:

Add '-10.66666667' to each side of the equation.
10.66666667 + 7x + -10.66666667 + x2 = 0 + -10.66666667

Reorder the terms:
10.66666667 + -10.66666667 + 7x + x2 = 0 + -10.66666667

Combine like terms: 10.66666667 + -10.66666667 = 0.00000000
0.00000000 + 7x + x2 = 0 + -10.66666667
7x + x2 = 0 + -10.66666667

Combine like terms: 0 + -10.66666667 = -10.66666667
7x + x2 = -10.66666667

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 = -10.66666667 + 12.25

Reorder the terms:
12.25 + 7x + x2 = -10.66666667 + 12.25

Combine like terms: -10.66666667 + 12.25 = 1.58333333
12.25 + 7x + x2 = 1.58333333

Factor a perfect square on the left side:
(x + 3.5)(x + 3.5) = 1.58333333

Calculate the square root of the right side: 1.258305738

Break this problem into two subproblems by setting 
(x + 3.5) equal to 1.258305738 and -1.258305738.

Subproblem 1

x + 3.5 = 1.258305738 Simplifying x + 3.5 = 1.258305738 Reorder the terms: 3.5 + x = 1.258305738 Solving 3.5 + x = 1.258305738 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 = 1.258305738 + -3.5 Combine like terms: 3.5 + -3.5 = 0.0 0.0 + x = 1.258305738 + -3.5 x = 1.258305738 + -3.5 Combine like terms: 1.258305738 + -3.5 = -2.241694262 x = -2.241694262 Simplifying x = -2.241694262

Subproblem 2

x + 3.5 = -1.258305738 Simplifying x + 3.5 = -1.258305738 Reorder the terms: 3.5 + x = -1.258305738 Solving 3.5 + x = -1.258305738 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 = -1.258305738 + -3.5 Combine like terms: 3.5 + -3.5 = 0.0 0.0 + x = -1.258305738 + -3.5 x = -1.258305738 + -3.5 Combine like terms: -1.258305738 + -3.5 = -4.758305738 x = -4.758305738 Simplifying x = -4.758305738

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-2.241694262, -4.758305738}

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