x(2x+5)=8

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Solution for x(2x+5)=8 equation:


Simplifying
x(2x + 5) = 8

Reorder the terms:
x(5 + 2x) = 8
(5 * x + 2x * x) = 8
(5x + 2x2) = 8

Solving
5x + 2x2 = 8

Solving for variable 'x'.

Reorder the terms:
-8 + 5x + 2x2 = 8 + -8

Combine like terms: 8 + -8 = 0
-8 + 5x + 2x2 = 0

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

Divide each side by '2'.
-4 + 2.5x + x2 = 0

Move the constant term to the right:

Add '4' to each side of the equation.
-4 + 2.5x + 4 + x2 = 0 + 4

Reorder the terms:
-4 + 4 + 2.5x + x2 = 0 + 4

Combine like terms: -4 + 4 = 0
0 + 2.5x + x2 = 0 + 4
2.5x + x2 = 0 + 4

Combine like terms: 0 + 4 = 4
2.5x + x2 = 4

The x term is 2.5x.  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.
2.5x + 1.5625 + x2 = 4 + 1.5625

Reorder the terms:
1.5625 + 2.5x + x2 = 4 + 1.5625

Combine like terms: 4 + 1.5625 = 5.5625
1.5625 + 2.5x + x2 = 5.5625

Factor a perfect square on the left side:
(x + 1.25)(x + 1.25) = 5.5625

Calculate the square root of the right side: 2.358495283

Break this problem into two subproblems by setting 
(x + 1.25) equal to 2.358495283 and -2.358495283.

Subproblem 1

x + 1.25 = 2.358495283 Simplifying x + 1.25 = 2.358495283 Reorder the terms: 1.25 + x = 2.358495283 Solving 1.25 + x = 2.358495283 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.25' to each side of the equation. 1.25 + -1.25 + x = 2.358495283 + -1.25 Combine like terms: 1.25 + -1.25 = 0.00 0.00 + x = 2.358495283 + -1.25 x = 2.358495283 + -1.25 Combine like terms: 2.358495283 + -1.25 = 1.108495283 x = 1.108495283 Simplifying x = 1.108495283

Subproblem 2

x + 1.25 = -2.358495283 Simplifying x + 1.25 = -2.358495283 Reorder the terms: 1.25 + x = -2.358495283 Solving 1.25 + x = -2.358495283 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.25' to each side of the equation. 1.25 + -1.25 + x = -2.358495283 + -1.25 Combine like terms: 1.25 + -1.25 = 0.00 0.00 + x = -2.358495283 + -1.25 x = -2.358495283 + -1.25 Combine like terms: -2.358495283 + -1.25 = -3.608495283 x = -3.608495283 Simplifying x = -3.608495283

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.108495283, -3.608495283}

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