X^2-9X=15

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Solution for X^2-9X=15 equation:


Simplifying
X2 + -9X = 15

Reorder the terms:
-9X + X2 = 15

Solving
-9X + X2 = 15

Solving for variable 'X'.

Reorder the terms:
-15 + -9X + X2 = 15 + -15

Combine like terms: 15 + -15 = 0
-15 + -9X + X2 = 0

Begin completing the square.

Move the constant term to the right:

Add '15' to each side of the equation.
-15 + -9X + 15 + X2 = 0 + 15

Reorder the terms:
-15 + 15 + -9X + X2 = 0 + 15

Combine like terms: -15 + 15 = 0
0 + -9X + X2 = 0 + 15
-9X + X2 = 0 + 15

Combine like terms: 0 + 15 = 15
-9X + X2 = 15

The X term is -9X.  Take half its coefficient (-4.5).
Square it (20.25) and add it to both sides.

Add '20.25' to each side of the equation.
-9X + 20.25 + X2 = 15 + 20.25

Reorder the terms:
20.25 + -9X + X2 = 15 + 20.25

Combine like terms: 15 + 20.25 = 35.25
20.25 + -9X + X2 = 35.25

Factor a perfect square on the left side:
(X + -4.5)(X + -4.5) = 35.25

Calculate the square root of the right side: 5.937171044

Break this problem into two subproblems by setting 
(X + -4.5) equal to 5.937171044 and -5.937171044.

Subproblem 1

X + -4.5 = 5.937171044 Simplifying X + -4.5 = 5.937171044 Reorder the terms: -4.5 + X = 5.937171044 Solving -4.5 + X = 5.937171044 Solving for variable 'X'. Move all terms containing X to the left, all other terms to the right. Add '4.5' to each side of the equation. -4.5 + 4.5 + X = 5.937171044 + 4.5 Combine like terms: -4.5 + 4.5 = 0.0 0.0 + X = 5.937171044 + 4.5 X = 5.937171044 + 4.5 Combine like terms: 5.937171044 + 4.5 = 10.437171044 X = 10.437171044 Simplifying X = 10.437171044

Subproblem 2

X + -4.5 = -5.937171044 Simplifying X + -4.5 = -5.937171044 Reorder the terms: -4.5 + X = -5.937171044 Solving -4.5 + X = -5.937171044 Solving for variable 'X'. Move all terms containing X to the left, all other terms to the right. Add '4.5' to each side of the equation. -4.5 + 4.5 + X = -5.937171044 + 4.5 Combine like terms: -4.5 + 4.5 = 0.0 0.0 + X = -5.937171044 + 4.5 X = -5.937171044 + 4.5 Combine like terms: -5.937171044 + 4.5 = -1.437171044 X = -1.437171044 Simplifying X = -1.437171044

Solution

The solution to the problem is based on the solutions from the subproblems. X = {10.437171044, -1.437171044}

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