d^2+18d+81=13

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Solution for d^2+18d+81=13 equation:


Simplifying
d2 + 18d + 81 = 13

Reorder the terms:
81 + 18d + d2 = 13

Solving
81 + 18d + d2 = 13

Solving for variable 'd'.

Reorder the terms:
81 + -13 + 18d + d2 = 13 + -13

Combine like terms: 81 + -13 = 68
68 + 18d + d2 = 13 + -13

Combine like terms: 13 + -13 = 0
68 + 18d + d2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-68' to each side of the equation.
68 + 18d + -68 + d2 = 0 + -68

Reorder the terms:
68 + -68 + 18d + d2 = 0 + -68

Combine like terms: 68 + -68 = 0
0 + 18d + d2 = 0 + -68
18d + d2 = 0 + -68

Combine like terms: 0 + -68 = -68
18d + d2 = -68

The d term is 18d.  Take half its coefficient (9).
Square it (81) and add it to both sides.

Add '81' to each side of the equation.
18d + 81 + d2 = -68 + 81

Reorder the terms:
81 + 18d + d2 = -68 + 81

Combine like terms: -68 + 81 = 13
81 + 18d + d2 = 13

Factor a perfect square on the left side:
(d + 9)(d + 9) = 13

Calculate the square root of the right side: 3.605551275

Break this problem into two subproblems by setting 
(d + 9) equal to 3.605551275 and -3.605551275.

Subproblem 1

d + 9 = 3.605551275 Simplifying d + 9 = 3.605551275 Reorder the terms: 9 + d = 3.605551275 Solving 9 + d = 3.605551275 Solving for variable 'd'. Move all terms containing d to the left, all other terms to the right. Add '-9' to each side of the equation. 9 + -9 + d = 3.605551275 + -9 Combine like terms: 9 + -9 = 0 0 + d = 3.605551275 + -9 d = 3.605551275 + -9 Combine like terms: 3.605551275 + -9 = -5.394448725 d = -5.394448725 Simplifying d = -5.394448725

Subproblem 2

d + 9 = -3.605551275 Simplifying d + 9 = -3.605551275 Reorder the terms: 9 + d = -3.605551275 Solving 9 + d = -3.605551275 Solving for variable 'd'. Move all terms containing d to the left, all other terms to the right. Add '-9' to each side of the equation. 9 + -9 + d = -3.605551275 + -9 Combine like terms: 9 + -9 = 0 0 + d = -3.605551275 + -9 d = -3.605551275 + -9 Combine like terms: -3.605551275 + -9 = -12.605551275 d = -12.605551275 Simplifying d = -12.605551275

Solution

The solution to the problem is based on the solutions from the subproblems. d = {-5.394448725, -12.605551275}

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