4d^2+9d-81=0

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Solution for 4d^2+9d-81=0 equation:


Simplifying
4d2 + 9d + -81 = 0

Reorder the terms:
-81 + 9d + 4d2 = 0

Solving
-81 + 9d + 4d2 = 0

Solving for variable 'd'.

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

Divide each side by '4'.
-20.25 + 2.25d + d2 = 0

Move the constant term to the right:

Add '20.25' to each side of the equation.
-20.25 + 2.25d + 20.25 + d2 = 0 + 20.25

Reorder the terms:
-20.25 + 20.25 + 2.25d + d2 = 0 + 20.25

Combine like terms: -20.25 + 20.25 = 0.00
0.00 + 2.25d + d2 = 0 + 20.25
2.25d + d2 = 0 + 20.25

Combine like terms: 0 + 20.25 = 20.25
2.25d + d2 = 20.25

The d term is 2.25d.  Take half its coefficient (1.125).
Square it (1.265625) and add it to both sides.

Add '1.265625' to each side of the equation.
2.25d + 1.265625 + d2 = 20.25 + 1.265625

Reorder the terms:
1.265625 + 2.25d + d2 = 20.25 + 1.265625

Combine like terms: 20.25 + 1.265625 = 21.515625
1.265625 + 2.25d + d2 = 21.515625

Factor a perfect square on the left side:
(d + 1.125)(d + 1.125) = 21.515625

Calculate the square root of the right side: 4.638493829

Break this problem into two subproblems by setting 
(d + 1.125) equal to 4.638493829 and -4.638493829.

Subproblem 1

d + 1.125 = 4.638493829 Simplifying d + 1.125 = 4.638493829 Reorder the terms: 1.125 + d = 4.638493829 Solving 1.125 + d = 4.638493829 Solving for variable 'd'. Move all terms containing d to the left, all other terms to the right. Add '-1.125' to each side of the equation. 1.125 + -1.125 + d = 4.638493829 + -1.125 Combine like terms: 1.125 + -1.125 = 0.000 0.000 + d = 4.638493829 + -1.125 d = 4.638493829 + -1.125 Combine like terms: 4.638493829 + -1.125 = 3.513493829 d = 3.513493829 Simplifying d = 3.513493829

Subproblem 2

d + 1.125 = -4.638493829 Simplifying d + 1.125 = -4.638493829 Reorder the terms: 1.125 + d = -4.638493829 Solving 1.125 + d = -4.638493829 Solving for variable 'd'. Move all terms containing d to the left, all other terms to the right. Add '-1.125' to each side of the equation. 1.125 + -1.125 + d = -4.638493829 + -1.125 Combine like terms: 1.125 + -1.125 = 0.000 0.000 + d = -4.638493829 + -1.125 d = -4.638493829 + -1.125 Combine like terms: -4.638493829 + -1.125 = -5.763493829 d = -5.763493829 Simplifying d = -5.763493829

Solution

The solution to the problem is based on the solutions from the subproblems. d = {3.513493829, -5.763493829}

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