7x^2+21x+6=

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Solution for 7x^2+21x+6= equation:


Simplifying
7x2 + 21x + 6 = 0

Reorder the terms:
6 + 21x + 7x2 = 0

Solving
6 + 21x + 7x2 = 0

Solving for variable 'x'.

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

Divide each side by '7'.
0.8571428571 + 3x + x2 = 0

Move the constant term to the right:

Add '-0.8571428571' to each side of the equation.
0.8571428571 + 3x + -0.8571428571 + x2 = 0 + -0.8571428571

Reorder the terms:
0.8571428571 + -0.8571428571 + 3x + x2 = 0 + -0.8571428571

Combine like terms: 0.8571428571 + -0.8571428571 = 0.0000000000
0.0000000000 + 3x + x2 = 0 + -0.8571428571
3x + x2 = 0 + -0.8571428571

Combine like terms: 0 + -0.8571428571 = -0.8571428571
3x + x2 = -0.8571428571

The x term is 3x.  Take half its coefficient (1.5).
Square it (2.25) and add it to both sides.

Add '2.25' to each side of the equation.
3x + 2.25 + x2 = -0.8571428571 + 2.25

Reorder the terms:
2.25 + 3x + x2 = -0.8571428571 + 2.25

Combine like terms: -0.8571428571 + 2.25 = 1.3928571429
2.25 + 3x + x2 = 1.3928571429

Factor a perfect square on the left side:
(x + 1.5)(x + 1.5) = 1.3928571429

Calculate the square root of the right side: 1.180193689

Break this problem into two subproblems by setting 
(x + 1.5) equal to 1.180193689 and -1.180193689.

Subproblem 1

x + 1.5 = 1.180193689 Simplifying x + 1.5 = 1.180193689 Reorder the terms: 1.5 + x = 1.180193689 Solving 1.5 + x = 1.180193689 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.5' to each side of the equation. 1.5 + -1.5 + x = 1.180193689 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = 1.180193689 + -1.5 x = 1.180193689 + -1.5 Combine like terms: 1.180193689 + -1.5 = -0.319806311 x = -0.319806311 Simplifying x = -0.319806311

Subproblem 2

x + 1.5 = -1.180193689 Simplifying x + 1.5 = -1.180193689 Reorder the terms: 1.5 + x = -1.180193689 Solving 1.5 + x = -1.180193689 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.5' to each side of the equation. 1.5 + -1.5 + x = -1.180193689 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = -1.180193689 + -1.5 x = -1.180193689 + -1.5 Combine like terms: -1.180193689 + -1.5 = -2.680193689 x = -2.680193689 Simplifying x = -2.680193689

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-0.319806311, -2.680193689}

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