-5x^2+28x+40=0

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Solution for -5x^2+28x+40=0 equation:


Simplifying
-5x2 + 28x + 40 = 0

Reorder the terms:
40 + 28x + -5x2 = 0

Solving
40 + 28x + -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 + -5.6x + x2 = 0

Move the constant term to the right:

Add '8' to each side of the equation.
-8 + -5.6x + 8 + x2 = 0 + 8

Reorder the terms:
-8 + 8 + -5.6x + x2 = 0 + 8

Combine like terms: -8 + 8 = 0
0 + -5.6x + x2 = 0 + 8
-5.6x + x2 = 0 + 8

Combine like terms: 0 + 8 = 8
-5.6x + x2 = 8

The x term is -5.6x.  Take half its coefficient (-2.8).
Square it (7.84) and add it to both sides.

Add '7.84' to each side of the equation.
-5.6x + 7.84 + x2 = 8 + 7.84

Reorder the terms:
7.84 + -5.6x + x2 = 8 + 7.84

Combine like terms: 8 + 7.84 = 15.84
7.84 + -5.6x + x2 = 15.84

Factor a perfect square on the left side:
(x + -2.8)(x + -2.8) = 15.84

Calculate the square root of the right side: 3.979949748

Break this problem into two subproblems by setting 
(x + -2.8) equal to 3.979949748 and -3.979949748.

Subproblem 1

x + -2.8 = 3.979949748 Simplifying x + -2.8 = 3.979949748 Reorder the terms: -2.8 + x = 3.979949748 Solving -2.8 + x = 3.979949748 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.8' to each side of the equation. -2.8 + 2.8 + x = 3.979949748 + 2.8 Combine like terms: -2.8 + 2.8 = 0.0 0.0 + x = 3.979949748 + 2.8 x = 3.979949748 + 2.8 Combine like terms: 3.979949748 + 2.8 = 6.779949748 x = 6.779949748 Simplifying x = 6.779949748

Subproblem 2

x + -2.8 = -3.979949748 Simplifying x + -2.8 = -3.979949748 Reorder the terms: -2.8 + x = -3.979949748 Solving -2.8 + x = -3.979949748 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.8' to each side of the equation. -2.8 + 2.8 + x = -3.979949748 + 2.8 Combine like terms: -2.8 + 2.8 = 0.0 0.0 + x = -3.979949748 + 2.8 x = -3.979949748 + 2.8 Combine like terms: -3.979949748 + 2.8 = -1.179949748 x = -1.179949748 Simplifying x = -1.179949748

Solution

The solution to the problem is based on the solutions from the subproblems. x = {6.779949748, -1.179949748}

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