5j^2+4j-8=0

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Solution for 5j^2+4j-8=0 equation:


Simplifying
5j2 + 4j + -8 = 0

Reorder the terms:
-8 + 4j + 5j2 = 0

Solving
-8 + 4j + 5j2 = 0

Solving for variable 'j'.

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

Divide each side by '5'.
-1.6 + 0.8j + j2 = 0

Move the constant term to the right:

Add '1.6' to each side of the equation.
-1.6 + 0.8j + 1.6 + j2 = 0 + 1.6

Reorder the terms:
-1.6 + 1.6 + 0.8j + j2 = 0 + 1.6

Combine like terms: -1.6 + 1.6 = 0.0
0.0 + 0.8j + j2 = 0 + 1.6
0.8j + j2 = 0 + 1.6

Combine like terms: 0 + 1.6 = 1.6
0.8j + j2 = 1.6

The j term is 0.8j.  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.
0.8j + 0.16 + j2 = 1.6 + 0.16

Reorder the terms:
0.16 + 0.8j + j2 = 1.6 + 0.16

Combine like terms: 1.6 + 0.16 = 1.76
0.16 + 0.8j + j2 = 1.76

Factor a perfect square on the left side:
(j + 0.4)(j + 0.4) = 1.76

Calculate the square root of the right side: 1.326649916

Break this problem into two subproblems by setting 
(j + 0.4) equal to 1.326649916 and -1.326649916.

Subproblem 1

j + 0.4 = 1.326649916 Simplifying j + 0.4 = 1.326649916 Reorder the terms: 0.4 + j = 1.326649916 Solving 0.4 + j = 1.326649916 Solving for variable 'j'. Move all terms containing j to the left, all other terms to the right. Add '-0.4' to each side of the equation. 0.4 + -0.4 + j = 1.326649916 + -0.4 Combine like terms: 0.4 + -0.4 = 0.0 0.0 + j = 1.326649916 + -0.4 j = 1.326649916 + -0.4 Combine like terms: 1.326649916 + -0.4 = 0.926649916 j = 0.926649916 Simplifying j = 0.926649916

Subproblem 2

j + 0.4 = -1.326649916 Simplifying j + 0.4 = -1.326649916 Reorder the terms: 0.4 + j = -1.326649916 Solving 0.4 + j = -1.326649916 Solving for variable 'j'. Move all terms containing j to the left, all other terms to the right. Add '-0.4' to each side of the equation. 0.4 + -0.4 + j = -1.326649916 + -0.4 Combine like terms: 0.4 + -0.4 = 0.0 0.0 + j = -1.326649916 + -0.4 j = -1.326649916 + -0.4 Combine like terms: -1.326649916 + -0.4 = -1.726649916 j = -1.726649916 Simplifying j = -1.726649916

Solution

The solution to the problem is based on the solutions from the subproblems. j = {0.926649916, -1.726649916}

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