0=5n^2-39n-42

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Solution for 0=5n^2-39n-42 equation:


Simplifying
0 = 5n2 + -39n + -42

Reorder the terms:
0 = -42 + -39n + 5n2

Solving
0 = -42 + -39n + 5n2

Solving for variable 'n'.

Combine like terms: 0 + 42 = 42
42 + 39n + -5n2 = -42 + -39n + 5n2 + 42 + 39n + -5n2

Reorder the terms:
42 + 39n + -5n2 = -42 + 42 + -39n + 39n + 5n2 + -5n2

Combine like terms: -42 + 42 = 0
42 + 39n + -5n2 = 0 + -39n + 39n + 5n2 + -5n2
42 + 39n + -5n2 = -39n + 39n + 5n2 + -5n2

Combine like terms: -39n + 39n = 0
42 + 39n + -5n2 = 0 + 5n2 + -5n2
42 + 39n + -5n2 = 5n2 + -5n2

Combine like terms: 5n2 + -5n2 = 0
42 + 39n + -5n2 = 0

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

Divide each side by '-5'.
-8.4 + -7.8n + n2 = 0

Move the constant term to the right:

Add '8.4' to each side of the equation.
-8.4 + -7.8n + 8.4 + n2 = 0 + 8.4

Reorder the terms:
-8.4 + 8.4 + -7.8n + n2 = 0 + 8.4

Combine like terms: -8.4 + 8.4 = 0.0
0.0 + -7.8n + n2 = 0 + 8.4
-7.8n + n2 = 0 + 8.4

Combine like terms: 0 + 8.4 = 8.4
-7.8n + n2 = 8.4

The n term is -7.8n.  Take half its coefficient (-3.9).
Square it (15.21) and add it to both sides.

Add '15.21' to each side of the equation.
-7.8n + 15.21 + n2 = 8.4 + 15.21

Reorder the terms:
15.21 + -7.8n + n2 = 8.4 + 15.21

Combine like terms: 8.4 + 15.21 = 23.61
15.21 + -7.8n + n2 = 23.61

Factor a perfect square on the left side:
(n + -3.9)(n + -3.9) = 23.61

Calculate the square root of the right side: 4.859012245

Break this problem into two subproblems by setting 
(n + -3.9) equal to 4.859012245 and -4.859012245.

Subproblem 1

n + -3.9 = 4.859012245 Simplifying n + -3.9 = 4.859012245 Reorder the terms: -3.9 + n = 4.859012245 Solving -3.9 + n = 4.859012245 Solving for variable 'n'. Move all terms containing n to the left, all other terms to the right. Add '3.9' to each side of the equation. -3.9 + 3.9 + n = 4.859012245 + 3.9 Combine like terms: -3.9 + 3.9 = 0.0 0.0 + n = 4.859012245 + 3.9 n = 4.859012245 + 3.9 Combine like terms: 4.859012245 + 3.9 = 8.759012245 n = 8.759012245 Simplifying n = 8.759012245

Subproblem 2

n + -3.9 = -4.859012245 Simplifying n + -3.9 = -4.859012245 Reorder the terms: -3.9 + n = -4.859012245 Solving -3.9 + n = -4.859012245 Solving for variable 'n'. Move all terms containing n to the left, all other terms to the right. Add '3.9' to each side of the equation. -3.9 + 3.9 + n = -4.859012245 + 3.9 Combine like terms: -3.9 + 3.9 = 0.0 0.0 + n = -4.859012245 + 3.9 n = -4.859012245 + 3.9 Combine like terms: -4.859012245 + 3.9 = -0.959012245 n = -0.959012245 Simplifying n = -0.959012245

Solution

The solution to the problem is based on the solutions from the subproblems. n = {8.759012245, -0.959012245}

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