3x^2-5x-7=20

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Solution for 3x^2-5x-7=20 equation:


Simplifying
3x2 + -5x + -7 = 20

Reorder the terms:
-7 + -5x + 3x2 = 20

Solving
-7 + -5x + 3x2 = 20

Solving for variable 'x'.

Reorder the terms:
-7 + -20 + -5x + 3x2 = 20 + -20

Combine like terms: -7 + -20 = -27
-27 + -5x + 3x2 = 20 + -20

Combine like terms: 20 + -20 = 0
-27 + -5x + 3x2 = 0

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

Divide each side by '3'.
-9 + -1.666666667x + x2 = 0

Move the constant term to the right:

Add '9' to each side of the equation.
-9 + -1.666666667x + 9 + x2 = 0 + 9

Reorder the terms:
-9 + 9 + -1.666666667x + x2 = 0 + 9

Combine like terms: -9 + 9 = 0
0 + -1.666666667x + x2 = 0 + 9
-1.666666667x + x2 = 0 + 9

Combine like terms: 0 + 9 = 9
-1.666666667x + x2 = 9

The x term is -1.666666667x.  Take half its coefficient (-0.8333333335).
Square it (0.6944444447) and add it to both sides.

Add '0.6944444447' to each side of the equation.
-1.666666667x + 0.6944444447 + x2 = 9 + 0.6944444447

Reorder the terms:
0.6944444447 + -1.666666667x + x2 = 9 + 0.6944444447

Combine like terms: 9 + 0.6944444447 = 9.6944444447
0.6944444447 + -1.666666667x + x2 = 9.6944444447

Factor a perfect square on the left side:
(x + -0.8333333335)(x + -0.8333333335) = 9.6944444447

Calculate the square root of the right side: 3.113590282

Break this problem into two subproblems by setting 
(x + -0.8333333335) equal to 3.113590282 and -3.113590282.

Subproblem 1

x + -0.8333333335 = 3.113590282 Simplifying x + -0.8333333335 = 3.113590282 Reorder the terms: -0.8333333335 + x = 3.113590282 Solving -0.8333333335 + x = 3.113590282 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.8333333335' to each side of the equation. -0.8333333335 + 0.8333333335 + x = 3.113590282 + 0.8333333335 Combine like terms: -0.8333333335 + 0.8333333335 = 0.0000000000 0.0000000000 + x = 3.113590282 + 0.8333333335 x = 3.113590282 + 0.8333333335 Combine like terms: 3.113590282 + 0.8333333335 = 3.9469236155 x = 3.9469236155 Simplifying x = 3.9469236155

Subproblem 2

x + -0.8333333335 = -3.113590282 Simplifying x + -0.8333333335 = -3.113590282 Reorder the terms: -0.8333333335 + x = -3.113590282 Solving -0.8333333335 + x = -3.113590282 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.8333333335' to each side of the equation. -0.8333333335 + 0.8333333335 + x = -3.113590282 + 0.8333333335 Combine like terms: -0.8333333335 + 0.8333333335 = 0.0000000000 0.0000000000 + x = -3.113590282 + 0.8333333335 x = -3.113590282 + 0.8333333335 Combine like terms: -3.113590282 + 0.8333333335 = -2.2802569485 x = -2.2802569485 Simplifying x = -2.2802569485

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.9469236155, -2.2802569485}

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