5x^2+8x-11=7

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Solution for 5x^2+8x-11=7 equation:


Simplifying
5x2 + 8x + -11 = 7

Reorder the terms:
-11 + 8x + 5x2 = 7

Solving
-11 + 8x + 5x2 = 7

Solving for variable 'x'.

Reorder the terms:
-11 + -7 + 8x + 5x2 = 7 + -7

Combine like terms: -11 + -7 = -18
-18 + 8x + 5x2 = 7 + -7

Combine like terms: 7 + -7 = 0
-18 + 8x + 5x2 = 0

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

Divide each side by '5'.
-3.6 + 1.6x + x2 = 0

Move the constant term to the right:

Add '3.6' to each side of the equation.
-3.6 + 1.6x + 3.6 + x2 = 0 + 3.6

Reorder the terms:
-3.6 + 3.6 + 1.6x + x2 = 0 + 3.6

Combine like terms: -3.6 + 3.6 = 0.0
0.0 + 1.6x + x2 = 0 + 3.6
1.6x + x2 = 0 + 3.6

Combine like terms: 0 + 3.6 = 3.6
1.6x + x2 = 3.6

The x term is 1.6x.  Take half its coefficient (0.8).
Square it (0.64) and add it to both sides.

Add '0.64' to each side of the equation.
1.6x + 0.64 + x2 = 3.6 + 0.64

Reorder the terms:
0.64 + 1.6x + x2 = 3.6 + 0.64

Combine like terms: 3.6 + 0.64 = 4.24
0.64 + 1.6x + x2 = 4.24

Factor a perfect square on the left side:
(x + 0.8)(x + 0.8) = 4.24

Calculate the square root of the right side: 2.059126028

Break this problem into two subproblems by setting 
(x + 0.8) equal to 2.059126028 and -2.059126028.

Subproblem 1

x + 0.8 = 2.059126028 Simplifying x + 0.8 = 2.059126028 Reorder the terms: 0.8 + x = 2.059126028 Solving 0.8 + x = 2.059126028 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.8' to each side of the equation. 0.8 + -0.8 + x = 2.059126028 + -0.8 Combine like terms: 0.8 + -0.8 = 0.0 0.0 + x = 2.059126028 + -0.8 x = 2.059126028 + -0.8 Combine like terms: 2.059126028 + -0.8 = 1.259126028 x = 1.259126028 Simplifying x = 1.259126028

Subproblem 2

x + 0.8 = -2.059126028 Simplifying x + 0.8 = -2.059126028 Reorder the terms: 0.8 + x = -2.059126028 Solving 0.8 + x = -2.059126028 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.8' to each side of the equation. 0.8 + -0.8 + x = -2.059126028 + -0.8 Combine like terms: 0.8 + -0.8 = 0.0 0.0 + x = -2.059126028 + -0.8 x = -2.059126028 + -0.8 Combine like terms: -2.059126028 + -0.8 = -2.859126028 x = -2.859126028 Simplifying x = -2.859126028

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.259126028, -2.859126028}

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