4k^2+8k-9=0

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Solution for 4k^2+8k-9=0 equation:


Simplifying
4k2 + 8k + -9 = 0

Reorder the terms:
-9 + 8k + 4k2 = 0

Solving
-9 + 8k + 4k2 = 0

Solving for variable 'k'.

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

Divide each side by '4'.
-2.25 + 2k + k2 = 0

Move the constant term to the right:

Add '2.25' to each side of the equation.
-2.25 + 2k + 2.25 + k2 = 0 + 2.25

Reorder the terms:
-2.25 + 2.25 + 2k + k2 = 0 + 2.25

Combine like terms: -2.25 + 2.25 = 0.00
0.00 + 2k + k2 = 0 + 2.25
2k + k2 = 0 + 2.25

Combine like terms: 0 + 2.25 = 2.25
2k + k2 = 2.25

The k term is 2k.  Take half its coefficient (1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
2k + 1 + k2 = 2.25 + 1

Reorder the terms:
1 + 2k + k2 = 2.25 + 1

Combine like terms: 2.25 + 1 = 3.25
1 + 2k + k2 = 3.25

Factor a perfect square on the left side:
(k + 1)(k + 1) = 3.25

Calculate the square root of the right side: 1.802775638

Break this problem into two subproblems by setting 
(k + 1) equal to 1.802775638 and -1.802775638.

Subproblem 1

k + 1 = 1.802775638 Simplifying k + 1 = 1.802775638 Reorder the terms: 1 + k = 1.802775638 Solving 1 + k = 1.802775638 Solving for variable 'k'. Move all terms containing k to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + k = 1.802775638 + -1 Combine like terms: 1 + -1 = 0 0 + k = 1.802775638 + -1 k = 1.802775638 + -1 Combine like terms: 1.802775638 + -1 = 0.802775638 k = 0.802775638 Simplifying k = 0.802775638

Subproblem 2

k + 1 = -1.802775638 Simplifying k + 1 = -1.802775638 Reorder the terms: 1 + k = -1.802775638 Solving 1 + k = -1.802775638 Solving for variable 'k'. Move all terms containing k to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + k = -1.802775638 + -1 Combine like terms: 1 + -1 = 0 0 + k = -1.802775638 + -1 k = -1.802775638 + -1 Combine like terms: -1.802775638 + -1 = -2.802775638 k = -2.802775638 Simplifying k = -2.802775638

Solution

The solution to the problem is based on the solutions from the subproblems. k = {0.802775638, -2.802775638}

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