8x^2+21x-45=0

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Solution for 8x^2+21x-45=0 equation:


Simplifying
8x2 + 21x + -45 = 0

Reorder the terms:
-45 + 21x + 8x2 = 0

Solving
-45 + 21x + 8x2 = 0

Solving for variable 'x'.

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

Divide each side by '8'.
-5.625 + 2.625x + x2 = 0

Move the constant term to the right:

Add '5.625' to each side of the equation.
-5.625 + 2.625x + 5.625 + x2 = 0 + 5.625

Reorder the terms:
-5.625 + 5.625 + 2.625x + x2 = 0 + 5.625

Combine like terms: -5.625 + 5.625 = 0.000
0.000 + 2.625x + x2 = 0 + 5.625
2.625x + x2 = 0 + 5.625

Combine like terms: 0 + 5.625 = 5.625
2.625x + x2 = 5.625

The x term is 2.625x.  Take half its coefficient (1.3125).
Square it (1.72265625) and add it to both sides.

Add '1.72265625' to each side of the equation.
2.625x + 1.72265625 + x2 = 5.625 + 1.72265625

Reorder the terms:
1.72265625 + 2.625x + x2 = 5.625 + 1.72265625

Combine like terms: 5.625 + 1.72265625 = 7.34765625
1.72265625 + 2.625x + x2 = 7.34765625

Factor a perfect square on the left side:
(x + 1.3125)(x + 1.3125) = 7.34765625

Calculate the square root of the right side: 2.710656055

Break this problem into two subproblems by setting 
(x + 1.3125) equal to 2.710656055 and -2.710656055.

Subproblem 1

x + 1.3125 = 2.710656055 Simplifying x + 1.3125 = 2.710656055 Reorder the terms: 1.3125 + x = 2.710656055 Solving 1.3125 + x = 2.710656055 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.3125' to each side of the equation. 1.3125 + -1.3125 + x = 2.710656055 + -1.3125 Combine like terms: 1.3125 + -1.3125 = 0.0000 0.0000 + x = 2.710656055 + -1.3125 x = 2.710656055 + -1.3125 Combine like terms: 2.710656055 + -1.3125 = 1.398156055 x = 1.398156055 Simplifying x = 1.398156055

Subproblem 2

x + 1.3125 = -2.710656055 Simplifying x + 1.3125 = -2.710656055 Reorder the terms: 1.3125 + x = -2.710656055 Solving 1.3125 + x = -2.710656055 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.3125' to each side of the equation. 1.3125 + -1.3125 + x = -2.710656055 + -1.3125 Combine like terms: 1.3125 + -1.3125 = 0.0000 0.0000 + x = -2.710656055 + -1.3125 x = -2.710656055 + -1.3125 Combine like terms: -2.710656055 + -1.3125 = -4.023156055 x = -4.023156055 Simplifying x = -4.023156055

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.398156055, -4.023156055}

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