(5X^2-7X-21)+(6X^2+9X)=

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Solution for (5X^2-7X-21)+(6X^2+9X)= equation:


Simplifying
(5X2 + -7X + -21) + (6X2 + 9X) = 0

Reorder the terms:
(-21 + -7X + 5X2) + (6X2 + 9X) = 0

Remove parenthesis around (-21 + -7X + 5X2)
-21 + -7X + 5X2 + (6X2 + 9X) = 0

Reorder the terms:
-21 + -7X + 5X2 + (9X + 6X2) = 0

Remove parenthesis around (9X + 6X2)
-21 + -7X + 5X2 + 9X + 6X2 = 0

Reorder the terms:
-21 + -7X + 9X + 5X2 + 6X2 = 0

Combine like terms: -7X + 9X = 2X
-21 + 2X + 5X2 + 6X2 = 0

Combine like terms: 5X2 + 6X2 = 11X2
-21 + 2X + 11X2 = 0

Solving
-21 + 2X + 11X2 = 0

Solving for variable 'X'.

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

Divide each side by '11'.
-1.909090909 + 0.1818181818X + X2 = 0

Move the constant term to the right:

Add '1.909090909' to each side of the equation.
-1.909090909 + 0.1818181818X + 1.909090909 + X2 = 0 + 1.909090909

Reorder the terms:
-1.909090909 + 1.909090909 + 0.1818181818X + X2 = 0 + 1.909090909

Combine like terms: -1.909090909 + 1.909090909 = 0.000000000
0.000000000 + 0.1818181818X + X2 = 0 + 1.909090909
0.1818181818X + X2 = 0 + 1.909090909

Combine like terms: 0 + 1.909090909 = 1.909090909
0.1818181818X + X2 = 1.909090909

The X term is 0.1818181818X.  Take half its coefficient (0.0909090909).
Square it (0.008264462808) and add it to both sides.

Add '0.008264462808' to each side of the equation.
0.1818181818X + 0.008264462808 + X2 = 1.909090909 + 0.008264462808

Reorder the terms:
0.008264462808 + 0.1818181818X + X2 = 1.909090909 + 0.008264462808

Combine like terms: 1.909090909 + 0.008264462808 = 1.917355371808
0.008264462808 + 0.1818181818X + X2 = 1.917355371808

Factor a perfect square on the left side:
(X + 0.0909090909)(X + 0.0909090909) = 1.917355371808

Calculate the square root of the right side: 1.384686019

Break this problem into two subproblems by setting 
(X + 0.0909090909) equal to 1.384686019 and -1.384686019.

Subproblem 1

X + 0.0909090909 = 1.384686019 Simplifying X + 0.0909090909 = 1.384686019 Reorder the terms: 0.0909090909 + X = 1.384686019 Solving 0.0909090909 + X = 1.384686019 Solving for variable 'X'. Move all terms containing X to the left, all other terms to the right. Add '-0.0909090909' to each side of the equation. 0.0909090909 + -0.0909090909 + X = 1.384686019 + -0.0909090909 Combine like terms: 0.0909090909 + -0.0909090909 = 0.0000000000 0.0000000000 + X = 1.384686019 + -0.0909090909 X = 1.384686019 + -0.0909090909 Combine like terms: 1.384686019 + -0.0909090909 = 1.2937769281 X = 1.2937769281 Simplifying X = 1.2937769281

Subproblem 2

X + 0.0909090909 = -1.384686019 Simplifying X + 0.0909090909 = -1.384686019 Reorder the terms: 0.0909090909 + X = -1.384686019 Solving 0.0909090909 + X = -1.384686019 Solving for variable 'X'. Move all terms containing X to the left, all other terms to the right. Add '-0.0909090909' to each side of the equation. 0.0909090909 + -0.0909090909 + X = -1.384686019 + -0.0909090909 Combine like terms: 0.0909090909 + -0.0909090909 = 0.0000000000 0.0000000000 + X = -1.384686019 + -0.0909090909 X = -1.384686019 + -0.0909090909 Combine like terms: -1.384686019 + -0.0909090909 = -1.4755951099 X = -1.4755951099 Simplifying X = -1.4755951099

Solution

The solution to the problem is based on the solutions from the subproblems. X = {1.2937769281, -1.4755951099}

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