5x^2-7x-40=0

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Solution for 5x^2-7x-40=0 equation:


Simplifying
5x2 + -7x + -40 = 0

Reorder the terms:
-40 + -7x + 5x2 = 0

Solving
-40 + -7x + 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'.
-8 + -1.4x + x2 = 0

Move the constant term to the right:

Add '8' to each side of the equation.
-8 + -1.4x + 8 + x2 = 0 + 8

Reorder the terms:
-8 + 8 + -1.4x + x2 = 0 + 8

Combine like terms: -8 + 8 = 0
0 + -1.4x + x2 = 0 + 8
-1.4x + x2 = 0 + 8

Combine like terms: 0 + 8 = 8
-1.4x + x2 = 8

The x term is -1.4x.  Take half its coefficient (-0.7).
Square it (0.49) and add it to both sides.

Add '0.49' to each side of the equation.
-1.4x + 0.49 + x2 = 8 + 0.49

Reorder the terms:
0.49 + -1.4x + x2 = 8 + 0.49

Combine like terms: 8 + 0.49 = 8.49
0.49 + -1.4x + x2 = 8.49

Factor a perfect square on the left side:
(x + -0.7)(x + -0.7) = 8.49

Calculate the square root of the right side: 2.913760457

Break this problem into two subproblems by setting 
(x + -0.7) equal to 2.913760457 and -2.913760457.

Subproblem 1

x + -0.7 = 2.913760457 Simplifying x + -0.7 = 2.913760457 Reorder the terms: -0.7 + x = 2.913760457 Solving -0.7 + x = 2.913760457 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.7' to each side of the equation. -0.7 + 0.7 + x = 2.913760457 + 0.7 Combine like terms: -0.7 + 0.7 = 0.0 0.0 + x = 2.913760457 + 0.7 x = 2.913760457 + 0.7 Combine like terms: 2.913760457 + 0.7 = 3.613760457 x = 3.613760457 Simplifying x = 3.613760457

Subproblem 2

x + -0.7 = -2.913760457 Simplifying x + -0.7 = -2.913760457 Reorder the terms: -0.7 + x = -2.913760457 Solving -0.7 + x = -2.913760457 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.7' to each side of the equation. -0.7 + 0.7 + x = -2.913760457 + 0.7 Combine like terms: -0.7 + 0.7 = 0.0 0.0 + x = -2.913760457 + 0.7 x = -2.913760457 + 0.7 Combine like terms: -2.913760457 + 0.7 = -2.213760457 x = -2.213760457 Simplifying x = -2.213760457

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.613760457, -2.213760457}

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