15x^2-12x-20=0

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Solution for 15x^2-12x-20=0 equation:


Simplifying
15x2 + -12x + -20 = 0

Reorder the terms:
-20 + -12x + 15x2 = 0

Solving
-20 + -12x + 15x2 = 0

Solving for variable 'x'.

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

Divide each side by '15'.
-1.333333333 + -0.8x + x2 = 0

Move the constant term to the right:

Add '1.333333333' to each side of the equation.
-1.333333333 + -0.8x + 1.333333333 + x2 = 0 + 1.333333333

Reorder the terms:
-1.333333333 + 1.333333333 + -0.8x + x2 = 0 + 1.333333333

Combine like terms: -1.333333333 + 1.333333333 = 0.000000000
0.000000000 + -0.8x + x2 = 0 + 1.333333333
-0.8x + x2 = 0 + 1.333333333

Combine like terms: 0 + 1.333333333 = 1.333333333
-0.8x + x2 = 1.333333333

The x term is -0.8x.  Take half its coefficient (-0.4).
Square it (0.16) and add it to both sides.

Add '0.16' to each side of the equation.
-0.8x + 0.16 + x2 = 1.333333333 + 0.16

Reorder the terms:
0.16 + -0.8x + x2 = 1.333333333 + 0.16

Combine like terms: 1.333333333 + 0.16 = 1.493333333
0.16 + -0.8x + x2 = 1.493333333

Factor a perfect square on the left side:
(x + -0.4)(x + -0.4) = 1.493333333

Calculate the square root of the right side: 1.222020185

Break this problem into two subproblems by setting 
(x + -0.4) equal to 1.222020185 and -1.222020185.

Subproblem 1

x + -0.4 = 1.222020185 Simplifying x + -0.4 = 1.222020185 Reorder the terms: -0.4 + x = 1.222020185 Solving -0.4 + x = 1.222020185 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.4' to each side of the equation. -0.4 + 0.4 + x = 1.222020185 + 0.4 Combine like terms: -0.4 + 0.4 = 0.0 0.0 + x = 1.222020185 + 0.4 x = 1.222020185 + 0.4 Combine like terms: 1.222020185 + 0.4 = 1.622020185 x = 1.622020185 Simplifying x = 1.622020185

Subproblem 2

x + -0.4 = -1.222020185 Simplifying x + -0.4 = -1.222020185 Reorder the terms: -0.4 + x = -1.222020185 Solving -0.4 + x = -1.222020185 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.4' to each side of the equation. -0.4 + 0.4 + x = -1.222020185 + 0.4 Combine like terms: -0.4 + 0.4 = 0.0 0.0 + x = -1.222020185 + 0.4 x = -1.222020185 + 0.4 Combine like terms: -1.222020185 + 0.4 = -0.822020185 x = -0.822020185 Simplifying x = -0.822020185

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.622020185, -0.822020185}

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