3x^2+8x^2-15x-40=0

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Solution for 3x^2+8x^2-15x-40=0 equation:


Simplifying
3x2 + 8x2 + -15x + -40 = 0

Reorder the terms:
-40 + -15x + 3x2 + 8x2 = 0

Combine like terms: 3x2 + 8x2 = 11x2
-40 + -15x + 11x2 = 0

Solving
-40 + -15x + 11x2 = 0

Solving for variable 'x'.

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

Divide each side by '11'.
-3.636363636 + -1.363636364x + x2 = 0

Move the constant term to the right:

Add '3.636363636' to each side of the equation.
-3.636363636 + -1.363636364x + 3.636363636 + x2 = 0 + 3.636363636

Reorder the terms:
-3.636363636 + 3.636363636 + -1.363636364x + x2 = 0 + 3.636363636

Combine like terms: -3.636363636 + 3.636363636 = 0.000000000
0.000000000 + -1.363636364x + x2 = 0 + 3.636363636
-1.363636364x + x2 = 0 + 3.636363636

Combine like terms: 0 + 3.636363636 = 3.636363636
-1.363636364x + x2 = 3.636363636

The x term is -1.363636364x.  Take half its coefficient (-0.681818182).
Square it (0.4648760333) and add it to both sides.

Add '0.4648760333' to each side of the equation.
-1.363636364x + 0.4648760333 + x2 = 3.636363636 + 0.4648760333

Reorder the terms:
0.4648760333 + -1.363636364x + x2 = 3.636363636 + 0.4648760333

Combine like terms: 3.636363636 + 0.4648760333 = 4.1012396693
0.4648760333 + -1.363636364x + x2 = 4.1012396693

Factor a perfect square on the left side:
(x + -0.681818182)(x + -0.681818182) = 4.1012396693

Calculate the square root of the right side: 2.025151765

Break this problem into two subproblems by setting 
(x + -0.681818182) equal to 2.025151765 and -2.025151765.

Subproblem 1

x + -0.681818182 = 2.025151765 Simplifying x + -0.681818182 = 2.025151765 Reorder the terms: -0.681818182 + x = 2.025151765 Solving -0.681818182 + x = 2.025151765 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.681818182' to each side of the equation. -0.681818182 + 0.681818182 + x = 2.025151765 + 0.681818182 Combine like terms: -0.681818182 + 0.681818182 = 0.000000000 0.000000000 + x = 2.025151765 + 0.681818182 x = 2.025151765 + 0.681818182 Combine like terms: 2.025151765 + 0.681818182 = 2.706969947 x = 2.706969947 Simplifying x = 2.706969947

Subproblem 2

x + -0.681818182 = -2.025151765 Simplifying x + -0.681818182 = -2.025151765 Reorder the terms: -0.681818182 + x = -2.025151765 Solving -0.681818182 + x = -2.025151765 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.681818182' to each side of the equation. -0.681818182 + 0.681818182 + x = -2.025151765 + 0.681818182 Combine like terms: -0.681818182 + 0.681818182 = 0.000000000 0.000000000 + x = -2.025151765 + 0.681818182 x = -2.025151765 + 0.681818182 Combine like terms: -2.025151765 + 0.681818182 = -1.343333583 x = -1.343333583 Simplifying x = -1.343333583

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.706969947, -1.343333583}

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