4x^2+20x-9=0

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Solution for 4x^2+20x-9=0 equation:


Simplifying
4x2 + 20x + -9 = 0

Reorder the terms:
-9 + 20x + 4x2 = 0

Solving
-9 + 20x + 4x2 = 0

Solving for variable 'x'.

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

Divide each side by '4'.
-2.25 + 5x + x2 = 0

Move the constant term to the right:

Add '2.25' to each side of the equation.
-2.25 + 5x + 2.25 + x2 = 0 + 2.25

Reorder the terms:
-2.25 + 2.25 + 5x + x2 = 0 + 2.25

Combine like terms: -2.25 + 2.25 = 0.00
0.00 + 5x + x2 = 0 + 2.25
5x + x2 = 0 + 2.25

Combine like terms: 0 + 2.25 = 2.25
5x + x2 = 2.25

The x term is 5x.  Take half its coefficient (2.5).
Square it (6.25) and add it to both sides.

Add '6.25' to each side of the equation.
5x + 6.25 + x2 = 2.25 + 6.25

Reorder the terms:
6.25 + 5x + x2 = 2.25 + 6.25

Combine like terms: 2.25 + 6.25 = 8.5
6.25 + 5x + x2 = 8.5

Factor a perfect square on the left side:
(x + 2.5)(x + 2.5) = 8.5

Calculate the square root of the right side: 2.915475947

Break this problem into two subproblems by setting 
(x + 2.5) equal to 2.915475947 and -2.915475947.

Subproblem 1

x + 2.5 = 2.915475947 Simplifying x + 2.5 = 2.915475947 Reorder the terms: 2.5 + x = 2.915475947 Solving 2.5 + x = 2.915475947 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.5' to each side of the equation. 2.5 + -2.5 + x = 2.915475947 + -2.5 Combine like terms: 2.5 + -2.5 = 0.0 0.0 + x = 2.915475947 + -2.5 x = 2.915475947 + -2.5 Combine like terms: 2.915475947 + -2.5 = 0.415475947 x = 0.415475947 Simplifying x = 0.415475947

Subproblem 2

x + 2.5 = -2.915475947 Simplifying x + 2.5 = -2.915475947 Reorder the terms: 2.5 + x = -2.915475947 Solving 2.5 + x = -2.915475947 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.5' to each side of the equation. 2.5 + -2.5 + x = -2.915475947 + -2.5 Combine like terms: 2.5 + -2.5 = 0.0 0.0 + x = -2.915475947 + -2.5 x = -2.915475947 + -2.5 Combine like terms: -2.915475947 + -2.5 = -5.415475947 x = -5.415475947 Simplifying x = -5.415475947

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.415475947, -5.415475947}

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