4x^2-x=15

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


Simplifying
4x2 + -1x = 15

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

Solving
-1x + 4x2 = 15

Solving for variable 'x'.

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

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

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

Divide each side by '4'.
-3.75 + -0.25x + x2 = 0

Move the constant term to the right:

Add '3.75' to each side of the equation.
-3.75 + -0.25x + 3.75 + x2 = 0 + 3.75

Reorder the terms:
-3.75 + 3.75 + -0.25x + x2 = 0 + 3.75

Combine like terms: -3.75 + 3.75 = 0.00
0.00 + -0.25x + x2 = 0 + 3.75
-0.25x + x2 = 0 + 3.75

Combine like terms: 0 + 3.75 = 3.75
-0.25x + x2 = 3.75

The x term is -0.25x.  Take half its coefficient (-0.125).
Square it (0.015625) and add it to both sides.

Add '0.015625' to each side of the equation.
-0.25x + 0.015625 + x2 = 3.75 + 0.015625

Reorder the terms:
0.015625 + -0.25x + x2 = 3.75 + 0.015625

Combine like terms: 3.75 + 0.015625 = 3.765625
0.015625 + -0.25x + x2 = 3.765625

Factor a perfect square on the left side:
(x + -0.125)(x + -0.125) = 3.765625

Calculate the square root of the right side: 1.940521837

Break this problem into two subproblems by setting 
(x + -0.125) equal to 1.940521837 and -1.940521837.

Subproblem 1

x + -0.125 = 1.940521837 Simplifying x + -0.125 = 1.940521837 Reorder the terms: -0.125 + x = 1.940521837 Solving -0.125 + x = 1.940521837 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.125' to each side of the equation. -0.125 + 0.125 + x = 1.940521837 + 0.125 Combine like terms: -0.125 + 0.125 = 0.000 0.000 + x = 1.940521837 + 0.125 x = 1.940521837 + 0.125 Combine like terms: 1.940521837 + 0.125 = 2.065521837 x = 2.065521837 Simplifying x = 2.065521837

Subproblem 2

x + -0.125 = -1.940521837 Simplifying x + -0.125 = -1.940521837 Reorder the terms: -0.125 + x = -1.940521837 Solving -0.125 + x = -1.940521837 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.125' to each side of the equation. -0.125 + 0.125 + x = -1.940521837 + 0.125 Combine like terms: -0.125 + 0.125 = 0.000 0.000 + x = -1.940521837 + 0.125 x = -1.940521837 + 0.125 Combine like terms: -1.940521837 + 0.125 = -1.815521837 x = -1.815521837 Simplifying x = -1.815521837

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.065521837, -1.815521837}

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