15-x^2=4x

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Solution for 15-x^2=4x equation:


Simplifying
15 + -1x2 = 4x

Solving
15 + -1x2 = 4x

Solving for variable 'x'.

Reorder the terms:
15 + -4x + -1x2 = 4x + -4x

Combine like terms: 4x + -4x = 0
15 + -4x + -1x2 = 0

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
-15 + 4x + x2 = 0

Move the constant term to the right:

Add '15' to each side of the equation.
-15 + 4x + 15 + x2 = 0 + 15

Reorder the terms:
-15 + 15 + 4x + x2 = 0 + 15

Combine like terms: -15 + 15 = 0
0 + 4x + x2 = 0 + 15
4x + x2 = 0 + 15

Combine like terms: 0 + 15 = 15
4x + x2 = 15

The x term is 4x.  Take half its coefficient (2).
Square it (4) and add it to both sides.

Add '4' to each side of the equation.
4x + 4 + x2 = 15 + 4

Reorder the terms:
4 + 4x + x2 = 15 + 4

Combine like terms: 15 + 4 = 19
4 + 4x + x2 = 19

Factor a perfect square on the left side:
(x + 2)(x + 2) = 19

Calculate the square root of the right side: 4.358898944

Break this problem into two subproblems by setting 
(x + 2) equal to 4.358898944 and -4.358898944.

Subproblem 1

x + 2 = 4.358898944 Simplifying x + 2 = 4.358898944 Reorder the terms: 2 + x = 4.358898944 Solving 2 + x = 4.358898944 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2' to each side of the equation. 2 + -2 + x = 4.358898944 + -2 Combine like terms: 2 + -2 = 0 0 + x = 4.358898944 + -2 x = 4.358898944 + -2 Combine like terms: 4.358898944 + -2 = 2.358898944 x = 2.358898944 Simplifying x = 2.358898944

Subproblem 2

x + 2 = -4.358898944 Simplifying x + 2 = -4.358898944 Reorder the terms: 2 + x = -4.358898944 Solving 2 + x = -4.358898944 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2' to each side of the equation. 2 + -2 + x = -4.358898944 + -2 Combine like terms: 2 + -2 = 0 0 + x = -4.358898944 + -2 x = -4.358898944 + -2 Combine like terms: -4.358898944 + -2 = -6.358898944 x = -6.358898944 Simplifying x = -6.358898944

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.358898944, -6.358898944}

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