2x^2+5x-40=0

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Solution for 2x^2+5x-40=0 equation:


Simplifying
2x2 + 5x + -40 = 0

Reorder the terms:
-40 + 5x + 2x2 = 0

Solving
-40 + 5x + 2x2 = 0

Solving for variable 'x'.

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

Divide each side by '2'.
-20 + 2.5x + x2 = 0

Move the constant term to the right:

Add '20' to each side of the equation.
-20 + 2.5x + 20 + x2 = 0 + 20

Reorder the terms:
-20 + 20 + 2.5x + x2 = 0 + 20

Combine like terms: -20 + 20 = 0
0 + 2.5x + x2 = 0 + 20
2.5x + x2 = 0 + 20

Combine like terms: 0 + 20 = 20
2.5x + x2 = 20

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 = 20 + 1.5625

Reorder the terms:
1.5625 + 2.5x + x2 = 20 + 1.5625

Combine like terms: 20 + 1.5625 = 21.5625
1.5625 + 2.5x + x2 = 21.5625

Factor a perfect square on the left side:
(x + 1.25)(x + 1.25) = 21.5625

Calculate the square root of the right side: 4.643543905

Break this problem into two subproblems by setting 
(x + 1.25) equal to 4.643543905 and -4.643543905.

Subproblem 1

x + 1.25 = 4.643543905 Simplifying x + 1.25 = 4.643543905 Reorder the terms: 1.25 + x = 4.643543905 Solving 1.25 + x = 4.643543905 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 = 4.643543905 + -1.25 Combine like terms: 1.25 + -1.25 = 0.00 0.00 + x = 4.643543905 + -1.25 x = 4.643543905 + -1.25 Combine like terms: 4.643543905 + -1.25 = 3.393543905 x = 3.393543905 Simplifying x = 3.393543905

Subproblem 2

x + 1.25 = -4.643543905 Simplifying x + 1.25 = -4.643543905 Reorder the terms: 1.25 + x = -4.643543905 Solving 1.25 + x = -4.643543905 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 = -4.643543905 + -1.25 Combine like terms: 1.25 + -1.25 = 0.00 0.00 + x = -4.643543905 + -1.25 x = -4.643543905 + -1.25 Combine like terms: -4.643543905 + -1.25 = -5.893543905 x = -5.893543905 Simplifying x = -5.893543905

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.393543905, -5.893543905}

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