x^2-9x+2x+21=80

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Solution for x^2-9x+2x+21=80 equation:


Simplifying
x2 + -9x + 2x + 21 = 80

Reorder the terms:
21 + -9x + 2x + x2 = 80

Combine like terms: -9x + 2x = -7x
21 + -7x + x2 = 80

Solving
21 + -7x + x2 = 80

Solving for variable 'x'.

Reorder the terms:
21 + -80 + -7x + x2 = 80 + -80

Combine like terms: 21 + -80 = -59
-59 + -7x + x2 = 80 + -80

Combine like terms: 80 + -80 = 0
-59 + -7x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '59' to each side of the equation.
-59 + -7x + 59 + x2 = 0 + 59

Reorder the terms:
-59 + 59 + -7x + x2 = 0 + 59

Combine like terms: -59 + 59 = 0
0 + -7x + x2 = 0 + 59
-7x + x2 = 0 + 59

Combine like terms: 0 + 59 = 59
-7x + x2 = 59

The x term is -7x.  Take half its coefficient (-3.5).
Square it (12.25) and add it to both sides.

Add '12.25' to each side of the equation.
-7x + 12.25 + x2 = 59 + 12.25

Reorder the terms:
12.25 + -7x + x2 = 59 + 12.25

Combine like terms: 59 + 12.25 = 71.25
12.25 + -7x + x2 = 71.25

Factor a perfect square on the left side:
(x + -3.5)(x + -3.5) = 71.25

Calculate the square root of the right side: 8.440971508

Break this problem into two subproblems by setting 
(x + -3.5) equal to 8.440971508 and -8.440971508.

Subproblem 1

x + -3.5 = 8.440971508 Simplifying x + -3.5 = 8.440971508 Reorder the terms: -3.5 + x = 8.440971508 Solving -3.5 + x = 8.440971508 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.5' to each side of the equation. -3.5 + 3.5 + x = 8.440971508 + 3.5 Combine like terms: -3.5 + 3.5 = 0.0 0.0 + x = 8.440971508 + 3.5 x = 8.440971508 + 3.5 Combine like terms: 8.440971508 + 3.5 = 11.940971508 x = 11.940971508 Simplifying x = 11.940971508

Subproblem 2

x + -3.5 = -8.440971508 Simplifying x + -3.5 = -8.440971508 Reorder the terms: -3.5 + x = -8.440971508 Solving -3.5 + x = -8.440971508 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.5' to each side of the equation. -3.5 + 3.5 + x = -8.440971508 + 3.5 Combine like terms: -3.5 + 3.5 = 0.0 0.0 + x = -8.440971508 + 3.5 x = -8.440971508 + 3.5 Combine like terms: -8.440971508 + 3.5 = -4.940971508 x = -4.940971508 Simplifying x = -4.940971508

Solution

The solution to the problem is based on the solutions from the subproblems. x = {11.940971508, -4.940971508}

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