2a^2-5a-1=0

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Solution for 2a^2-5a-1=0 equation:


Simplifying
2a2 + -5a + -1 = 0

Reorder the terms:
-1 + -5a + 2a2 = 0

Solving
-1 + -5a + 2a2 = 0

Solving for variable 'a'.

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

Divide each side by '2'.
-0.5 + -2.5a + a2 = 0

Move the constant term to the right:

Add '0.5' to each side of the equation.
-0.5 + -2.5a + 0.5 + a2 = 0 + 0.5

Reorder the terms:
-0.5 + 0.5 + -2.5a + a2 = 0 + 0.5

Combine like terms: -0.5 + 0.5 = 0.0
0.0 + -2.5a + a2 = 0 + 0.5
-2.5a + a2 = 0 + 0.5

Combine like terms: 0 + 0.5 = 0.5
-2.5a + a2 = 0.5

The a term is -2.5a.  Take half its coefficient (-1.25).
Square it (1.5625) and add it to both sides.

Add '1.5625' to each side of the equation.
-2.5a + 1.5625 + a2 = 0.5 + 1.5625

Reorder the terms:
1.5625 + -2.5a + a2 = 0.5 + 1.5625

Combine like terms: 0.5 + 1.5625 = 2.0625
1.5625 + -2.5a + a2 = 2.0625

Factor a perfect square on the left side:
(a + -1.25)(a + -1.25) = 2.0625

Calculate the square root of the right side: 1.436140662

Break this problem into two subproblems by setting 
(a + -1.25) equal to 1.436140662 and -1.436140662.

Subproblem 1

a + -1.25 = 1.436140662 Simplifying a + -1.25 = 1.436140662 Reorder the terms: -1.25 + a = 1.436140662 Solving -1.25 + a = 1.436140662 Solving for variable 'a'. Move all terms containing a to the left, all other terms to the right. Add '1.25' to each side of the equation. -1.25 + 1.25 + a = 1.436140662 + 1.25 Combine like terms: -1.25 + 1.25 = 0.00 0.00 + a = 1.436140662 + 1.25 a = 1.436140662 + 1.25 Combine like terms: 1.436140662 + 1.25 = 2.686140662 a = 2.686140662 Simplifying a = 2.686140662

Subproblem 2

a + -1.25 = -1.436140662 Simplifying a + -1.25 = -1.436140662 Reorder the terms: -1.25 + a = -1.436140662 Solving -1.25 + a = -1.436140662 Solving for variable 'a'. Move all terms containing a to the left, all other terms to the right. Add '1.25' to each side of the equation. -1.25 + 1.25 + a = -1.436140662 + 1.25 Combine like terms: -1.25 + 1.25 = 0.00 0.00 + a = -1.436140662 + 1.25 a = -1.436140662 + 1.25 Combine like terms: -1.436140662 + 1.25 = -0.186140662 a = -0.186140662 Simplifying a = -0.186140662

Solution

The solution to the problem is based on the solutions from the subproblems. a = {2.686140662, -0.186140662}

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