5a^2-a-20=0

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Solution for 5a^2-a-20=0 equation:


Simplifying
5a2 + -1a + -20 = 0

Reorder the terms:
-20 + -1a + 5a2 = 0

Solving
-20 + -1a + 5a2 = 0

Solving for variable 'a'.

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

Divide each side by '5'.
-4 + -0.2a + a2 = 0

Move the constant term to the right:

Add '4' to each side of the equation.
-4 + -0.2a + 4 + a2 = 0 + 4

Reorder the terms:
-4 + 4 + -0.2a + a2 = 0 + 4

Combine like terms: -4 + 4 = 0
0 + -0.2a + a2 = 0 + 4
-0.2a + a2 = 0 + 4

Combine like terms: 0 + 4 = 4
-0.2a + a2 = 4

The a term is -0.2a.  Take half its coefficient (-0.1).
Square it (0.01) and add it to both sides.

Add '0.01' to each side of the equation.
-0.2a + 0.01 + a2 = 4 + 0.01

Reorder the terms:
0.01 + -0.2a + a2 = 4 + 0.01

Combine like terms: 4 + 0.01 = 4.01
0.01 + -0.2a + a2 = 4.01

Factor a perfect square on the left side:
(a + -0.1)(a + -0.1) = 4.01

Calculate the square root of the right side: 2.002498439

Break this problem into two subproblems by setting 
(a + -0.1) equal to 2.002498439 and -2.002498439.

Subproblem 1

a + -0.1 = 2.002498439 Simplifying a + -0.1 = 2.002498439 Reorder the terms: -0.1 + a = 2.002498439 Solving -0.1 + a = 2.002498439 Solving for variable 'a'. Move all terms containing a to the left, all other terms to the right. Add '0.1' to each side of the equation. -0.1 + 0.1 + a = 2.002498439 + 0.1 Combine like terms: -0.1 + 0.1 = 0.0 0.0 + a = 2.002498439 + 0.1 a = 2.002498439 + 0.1 Combine like terms: 2.002498439 + 0.1 = 2.102498439 a = 2.102498439 Simplifying a = 2.102498439

Subproblem 2

a + -0.1 = -2.002498439 Simplifying a + -0.1 = -2.002498439 Reorder the terms: -0.1 + a = -2.002498439 Solving -0.1 + a = -2.002498439 Solving for variable 'a'. Move all terms containing a to the left, all other terms to the right. Add '0.1' to each side of the equation. -0.1 + 0.1 + a = -2.002498439 + 0.1 Combine like terms: -0.1 + 0.1 = 0.0 0.0 + a = -2.002498439 + 0.1 a = -2.002498439 + 0.1 Combine like terms: -2.002498439 + 0.1 = -1.902498439 a = -1.902498439 Simplifying a = -1.902498439

Solution

The solution to the problem is based on the solutions from the subproblems. a = {2.102498439, -1.902498439}

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