4c^2+21c+15=

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Solution for 4c^2+21c+15= equation:


Simplifying
4c2 + 21c + 15 = 0

Reorder the terms:
15 + 21c + 4c2 = 0

Solving
15 + 21c + 4c2 = 0

Solving for variable 'c'.

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

Divide each side by '4'.
3.75 + 5.25c + c2 = 0

Move the constant term to the right:

Add '-3.75' to each side of the equation.
3.75 + 5.25c + -3.75 + c2 = 0 + -3.75

Reorder the terms:
3.75 + -3.75 + 5.25c + c2 = 0 + -3.75

Combine like terms: 3.75 + -3.75 = 0.00
0.00 + 5.25c + c2 = 0 + -3.75
5.25c + c2 = 0 + -3.75

Combine like terms: 0 + -3.75 = -3.75
5.25c + c2 = -3.75

The c term is 5.25c.  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.
5.25c + 6.890625 + c2 = -3.75 + 6.890625

Reorder the terms:
6.890625 + 5.25c + c2 = -3.75 + 6.890625

Combine like terms: -3.75 + 6.890625 = 3.140625
6.890625 + 5.25c + c2 = 3.140625

Factor a perfect square on the left side:
(c + 2.625)(c + 2.625) = 3.140625

Calculate the square root of the right side: 1.77218086

Break this problem into two subproblems by setting 
(c + 2.625) equal to 1.77218086 and -1.77218086.

Subproblem 1

c + 2.625 = 1.77218086 Simplifying c + 2.625 = 1.77218086 Reorder the terms: 2.625 + c = 1.77218086 Solving 2.625 + c = 1.77218086 Solving for variable 'c'. Move all terms containing c to the left, all other terms to the right. Add '-2.625' to each side of the equation. 2.625 + -2.625 + c = 1.77218086 + -2.625 Combine like terms: 2.625 + -2.625 = 0.000 0.000 + c = 1.77218086 + -2.625 c = 1.77218086 + -2.625 Combine like terms: 1.77218086 + -2.625 = -0.85281914 c = -0.85281914 Simplifying c = -0.85281914

Subproblem 2

c + 2.625 = -1.77218086 Simplifying c + 2.625 = -1.77218086 Reorder the terms: 2.625 + c = -1.77218086 Solving 2.625 + c = -1.77218086 Solving for variable 'c'. Move all terms containing c to the left, all other terms to the right. Add '-2.625' to each side of the equation. 2.625 + -2.625 + c = -1.77218086 + -2.625 Combine like terms: 2.625 + -2.625 = 0.000 0.000 + c = -1.77218086 + -2.625 c = -1.77218086 + -2.625 Combine like terms: -1.77218086 + -2.625 = -4.39718086 c = -4.39718086 Simplifying c = -4.39718086

Solution

The solution to the problem is based on the solutions from the subproblems. c = {-0.85281914, -4.39718086}

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