5d^2-7d-5=0

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Solution for 5d^2-7d-5=0 equation:


Simplifying
5d2 + -7d + -5 = 0

Reorder the terms:
-5 + -7d + 5d2 = 0

Solving
-5 + -7d + 5d2 = 0

Solving for variable 'd'.

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

Divide each side by '5'.
-1 + -1.4d + d2 = 0

Move the constant term to the right:

Add '1' to each side of the equation.
-1 + -1.4d + 1 + d2 = 0 + 1

Reorder the terms:
-1 + 1 + -1.4d + d2 = 0 + 1

Combine like terms: -1 + 1 = 0
0 + -1.4d + d2 = 0 + 1
-1.4d + d2 = 0 + 1

Combine like terms: 0 + 1 = 1
-1.4d + d2 = 1

The d term is -1.4d.  Take half its coefficient (-0.7).
Square it (0.49) and add it to both sides.

Add '0.49' to each side of the equation.
-1.4d + 0.49 + d2 = 1 + 0.49

Reorder the terms:
0.49 + -1.4d + d2 = 1 + 0.49

Combine like terms: 1 + 0.49 = 1.49
0.49 + -1.4d + d2 = 1.49

Factor a perfect square on the left side:
(d + -0.7)(d + -0.7) = 1.49

Calculate the square root of the right side: 1.220655562

Break this problem into two subproblems by setting 
(d + -0.7) equal to 1.220655562 and -1.220655562.

Subproblem 1

d + -0.7 = 1.220655562 Simplifying d + -0.7 = 1.220655562 Reorder the terms: -0.7 + d = 1.220655562 Solving -0.7 + d = 1.220655562 Solving for variable 'd'. Move all terms containing d to the left, all other terms to the right. Add '0.7' to each side of the equation. -0.7 + 0.7 + d = 1.220655562 + 0.7 Combine like terms: -0.7 + 0.7 = 0.0 0.0 + d = 1.220655562 + 0.7 d = 1.220655562 + 0.7 Combine like terms: 1.220655562 + 0.7 = 1.920655562 d = 1.920655562 Simplifying d = 1.920655562

Subproblem 2

d + -0.7 = -1.220655562 Simplifying d + -0.7 = -1.220655562 Reorder the terms: -0.7 + d = -1.220655562 Solving -0.7 + d = -1.220655562 Solving for variable 'd'. Move all terms containing d to the left, all other terms to the right. Add '0.7' to each side of the equation. -0.7 + 0.7 + d = -1.220655562 + 0.7 Combine like terms: -0.7 + 0.7 = 0.0 0.0 + d = -1.220655562 + 0.7 d = -1.220655562 + 0.7 Combine like terms: -1.220655562 + 0.7 = -0.520655562 d = -0.520655562 Simplifying d = -0.520655562

Solution

The solution to the problem is based on the solutions from the subproblems. d = {1.920655562, -0.520655562}

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