21x^2+144x+215=0

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Solution for 21x^2+144x+215=0 equation:


Simplifying
21x2 + 144x + 215 = 0

Reorder the terms:
215 + 144x + 21x2 = 0

Solving
215 + 144x + 21x2 = 0

Solving for variable 'x'.

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

Divide each side by '21'.
10.23809524 + 6.857142857x + x2 = 0

Move the constant term to the right:

Add '-10.23809524' to each side of the equation.
10.23809524 + 6.857142857x + -10.23809524 + x2 = 0 + -10.23809524

Reorder the terms:
10.23809524 + -10.23809524 + 6.857142857x + x2 = 0 + -10.23809524

Combine like terms: 10.23809524 + -10.23809524 = 0.00000000
0.00000000 + 6.857142857x + x2 = 0 + -10.23809524
6.857142857x + x2 = 0 + -10.23809524

Combine like terms: 0 + -10.23809524 = -10.23809524
6.857142857x + x2 = -10.23809524

The x term is 6.857142857x.  Take half its coefficient (3.428571429).
Square it (11.75510204) and add it to both sides.

Add '11.75510204' to each side of the equation.
6.857142857x + 11.75510204 + x2 = -10.23809524 + 11.75510204

Reorder the terms:
11.75510204 + 6.857142857x + x2 = -10.23809524 + 11.75510204

Combine like terms: -10.23809524 + 11.75510204 = 1.5170068
11.75510204 + 6.857142857x + x2 = 1.5170068

Factor a perfect square on the left side:
(x + 3.428571429)(x + 3.428571429) = 1.5170068

Calculate the square root of the right side: 1.2316683

Break this problem into two subproblems by setting 
(x + 3.428571429) equal to 1.2316683 and -1.2316683.

Subproblem 1

x + 3.428571429 = 1.2316683 Simplifying x + 3.428571429 = 1.2316683 Reorder the terms: 3.428571429 + x = 1.2316683 Solving 3.428571429 + x = 1.2316683 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.428571429' to each side of the equation. 3.428571429 + -3.428571429 + x = 1.2316683 + -3.428571429 Combine like terms: 3.428571429 + -3.428571429 = 0.000000000 0.000000000 + x = 1.2316683 + -3.428571429 x = 1.2316683 + -3.428571429 Combine like terms: 1.2316683 + -3.428571429 = -2.196903129 x = -2.196903129 Simplifying x = -2.196903129

Subproblem 2

x + 3.428571429 = -1.2316683 Simplifying x + 3.428571429 = -1.2316683 Reorder the terms: 3.428571429 + x = -1.2316683 Solving 3.428571429 + x = -1.2316683 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.428571429' to each side of the equation. 3.428571429 + -3.428571429 + x = -1.2316683 + -3.428571429 Combine like terms: 3.428571429 + -3.428571429 = 0.000000000 0.000000000 + x = -1.2316683 + -3.428571429 x = -1.2316683 + -3.428571429 Combine like terms: -1.2316683 + -3.428571429 = -4.660239729 x = -4.660239729 Simplifying x = -4.660239729

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-2.196903129, -4.660239729}

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