5x^2+4x-87=0

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Solution for 5x^2+4x-87=0 equation:


Simplifying
5x2 + 4x + -87 = 0

Reorder the terms:
-87 + 4x + 5x2 = 0

Solving
-87 + 4x + 5x2 = 0

Solving for variable 'x'.

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

Divide each side by '5'.
-17.4 + 0.8x + x2 = 0

Move the constant term to the right:

Add '17.4' to each side of the equation.
-17.4 + 0.8x + 17.4 + x2 = 0 + 17.4

Reorder the terms:
-17.4 + 17.4 + 0.8x + x2 = 0 + 17.4

Combine like terms: -17.4 + 17.4 = 0.0
0.0 + 0.8x + x2 = 0 + 17.4
0.8x + x2 = 0 + 17.4

Combine like terms: 0 + 17.4 = 17.4
0.8x + x2 = 17.4

The x term is 0.8x.  Take half its coefficient (0.4).
Square it (0.16) and add it to both sides.

Add '0.16' to each side of the equation.
0.8x + 0.16 + x2 = 17.4 + 0.16

Reorder the terms:
0.16 + 0.8x + x2 = 17.4 + 0.16

Combine like terms: 17.4 + 0.16 = 17.56
0.16 + 0.8x + x2 = 17.56

Factor a perfect square on the left side:
(x + 0.4)(x + 0.4) = 17.56

Calculate the square root of the right side: 4.190465368

Break this problem into two subproblems by setting 
(x + 0.4) equal to 4.190465368 and -4.190465368.

Subproblem 1

x + 0.4 = 4.190465368 Simplifying x + 0.4 = 4.190465368 Reorder the terms: 0.4 + x = 4.190465368 Solving 0.4 + x = 4.190465368 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.4' to each side of the equation. 0.4 + -0.4 + x = 4.190465368 + -0.4 Combine like terms: 0.4 + -0.4 = 0.0 0.0 + x = 4.190465368 + -0.4 x = 4.190465368 + -0.4 Combine like terms: 4.190465368 + -0.4 = 3.790465368 x = 3.790465368 Simplifying x = 3.790465368

Subproblem 2

x + 0.4 = -4.190465368 Simplifying x + 0.4 = -4.190465368 Reorder the terms: 0.4 + x = -4.190465368 Solving 0.4 + x = -4.190465368 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.4' to each side of the equation. 0.4 + -0.4 + x = -4.190465368 + -0.4 Combine like terms: 0.4 + -0.4 = 0.0 0.0 + x = -4.190465368 + -0.4 x = -4.190465368 + -0.4 Combine like terms: -4.190465368 + -0.4 = -4.590465368 x = -4.590465368 Simplifying x = -4.590465368

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.790465368, -4.590465368}

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