0=x^2+17x-21

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Solution for 0=x^2+17x-21 equation:


Simplifying
0 = x2 + 17x + -21

Reorder the terms:
0 = -21 + 17x + x2

Solving
0 = -21 + 17x + x2

Solving for variable 'x'.

Combine like terms: 0 + 21 = 21
21 + -17x + -1x2 = -21 + 17x + x2 + 21 + -17x + -1x2

Reorder the terms:
21 + -17x + -1x2 = -21 + 21 + 17x + -17x + x2 + -1x2

Combine like terms: -21 + 21 = 0
21 + -17x + -1x2 = 0 + 17x + -17x + x2 + -1x2
21 + -17x + -1x2 = 17x + -17x + x2 + -1x2

Combine like terms: 17x + -17x = 0
21 + -17x + -1x2 = 0 + x2 + -1x2
21 + -17x + -1x2 = x2 + -1x2

Combine like terms: x2 + -1x2 = 0
21 + -17x + -1x2 = 0

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
-21 + 17x + x2 = 0

Move the constant term to the right:

Add '21' to each side of the equation.
-21 + 17x + 21 + x2 = 0 + 21

Reorder the terms:
-21 + 21 + 17x + x2 = 0 + 21

Combine like terms: -21 + 21 = 0
0 + 17x + x2 = 0 + 21
17x + x2 = 0 + 21

Combine like terms: 0 + 21 = 21
17x + x2 = 21

The x term is 17x.  Take half its coefficient (8.5).
Square it (72.25) and add it to both sides.

Add '72.25' to each side of the equation.
17x + 72.25 + x2 = 21 + 72.25

Reorder the terms:
72.25 + 17x + x2 = 21 + 72.25

Combine like terms: 21 + 72.25 = 93.25
72.25 + 17x + x2 = 93.25

Factor a perfect square on the left side:
(x + 8.5)(x + 8.5) = 93.25

Calculate the square root of the right side: 9.656603958

Break this problem into two subproblems by setting 
(x + 8.5) equal to 9.656603958 and -9.656603958.

Subproblem 1

x + 8.5 = 9.656603958 Simplifying x + 8.5 = 9.656603958 Reorder the terms: 8.5 + x = 9.656603958 Solving 8.5 + x = 9.656603958 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-8.5' to each side of the equation. 8.5 + -8.5 + x = 9.656603958 + -8.5 Combine like terms: 8.5 + -8.5 = 0.0 0.0 + x = 9.656603958 + -8.5 x = 9.656603958 + -8.5 Combine like terms: 9.656603958 + -8.5 = 1.156603958 x = 1.156603958 Simplifying x = 1.156603958

Subproblem 2

x + 8.5 = -9.656603958 Simplifying x + 8.5 = -9.656603958 Reorder the terms: 8.5 + x = -9.656603958 Solving 8.5 + x = -9.656603958 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-8.5' to each side of the equation. 8.5 + -8.5 + x = -9.656603958 + -8.5 Combine like terms: 8.5 + -8.5 = 0.0 0.0 + x = -9.656603958 + -8.5 x = -9.656603958 + -8.5 Combine like terms: -9.656603958 + -8.5 = -18.156603958 x = -18.156603958 Simplifying x = -18.156603958

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.156603958, -18.156603958}

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