4x^2+21x+8=

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Solution for 4x^2+21x+8= equation:


Simplifying
4x2 + 21x + 8 = 0

Reorder the terms:
8 + 21x + 4x2 = 0

Solving
8 + 21x + 4x2 = 0

Solving for variable 'x'.

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

Divide each side by '4'.
2 + 5.25x + x2 = 0

Move the constant term to the right:

Add '-2' to each side of the equation.
2 + 5.25x + -2 + x2 = 0 + -2

Reorder the terms:
2 + -2 + 5.25x + x2 = 0 + -2

Combine like terms: 2 + -2 = 0
0 + 5.25x + x2 = 0 + -2
5.25x + x2 = 0 + -2

Combine like terms: 0 + -2 = -2
5.25x + x2 = -2

The x term is 5.25x.  Take half its coefficient (2.625).
Square it (6.890625) and add it to both sides.

Add '6.890625' to each side of the equation.
5.25x + 6.890625 + x2 = -2 + 6.890625

Reorder the terms:
6.890625 + 5.25x + x2 = -2 + 6.890625

Combine like terms: -2 + 6.890625 = 4.890625
6.890625 + 5.25x + x2 = 4.890625

Factor a perfect square on the left side:
(x + 2.625)(x + 2.625) = 4.890625

Calculate the square root of the right side: 2.211475752

Break this problem into two subproblems by setting 
(x + 2.625) equal to 2.211475752 and -2.211475752.

Subproblem 1

x + 2.625 = 2.211475752 Simplifying x + 2.625 = 2.211475752 Reorder the terms: 2.625 + x = 2.211475752 Solving 2.625 + x = 2.211475752 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.625' to each side of the equation. 2.625 + -2.625 + x = 2.211475752 + -2.625 Combine like terms: 2.625 + -2.625 = 0.000 0.000 + x = 2.211475752 + -2.625 x = 2.211475752 + -2.625 Combine like terms: 2.211475752 + -2.625 = -0.413524248 x = -0.413524248 Simplifying x = -0.413524248

Subproblem 2

x + 2.625 = -2.211475752 Simplifying x + 2.625 = -2.211475752 Reorder the terms: 2.625 + x = -2.211475752 Solving 2.625 + x = -2.211475752 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.625' to each side of the equation. 2.625 + -2.625 + x = -2.211475752 + -2.625 Combine like terms: 2.625 + -2.625 = 0.000 0.000 + x = -2.211475752 + -2.625 x = -2.211475752 + -2.625 Combine like terms: -2.211475752 + -2.625 = -4.836475752 x = -4.836475752 Simplifying x = -4.836475752

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-0.413524248, -4.836475752}

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