2x^2-14x+21=0

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Solution for 2x^2-14x+21=0 equation:


Simplifying
2x2 + -14x + 21 = 0

Reorder the terms:
21 + -14x + 2x2 = 0

Solving
21 + -14x + 2x2 = 0

Solving for variable 'x'.

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

Divide each side by '2'.
10.5 + -7x + x2 = 0

Move the constant term to the right:

Add '-10.5' to each side of the equation.
10.5 + -7x + -10.5 + x2 = 0 + -10.5

Reorder the terms:
10.5 + -10.5 + -7x + x2 = 0 + -10.5

Combine like terms: 10.5 + -10.5 = 0.0
0.0 + -7x + x2 = 0 + -10.5
-7x + x2 = 0 + -10.5

Combine like terms: 0 + -10.5 = -10.5
-7x + x2 = -10.5

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 = -10.5 + 12.25

Reorder the terms:
12.25 + -7x + x2 = -10.5 + 12.25

Combine like terms: -10.5 + 12.25 = 1.75
12.25 + -7x + x2 = 1.75

Factor a perfect square on the left side:
(x + -3.5)(x + -3.5) = 1.75

Calculate the square root of the right side: 1.322875656

Break this problem into two subproblems by setting 
(x + -3.5) equal to 1.322875656 and -1.322875656.

Subproblem 1

x + -3.5 = 1.322875656 Simplifying x + -3.5 = 1.322875656 Reorder the terms: -3.5 + x = 1.322875656 Solving -3.5 + x = 1.322875656 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 = 1.322875656 + 3.5 Combine like terms: -3.5 + 3.5 = 0.0 0.0 + x = 1.322875656 + 3.5 x = 1.322875656 + 3.5 Combine like terms: 1.322875656 + 3.5 = 4.822875656 x = 4.822875656 Simplifying x = 4.822875656

Subproblem 2

x + -3.5 = -1.322875656 Simplifying x + -3.5 = -1.322875656 Reorder the terms: -3.5 + x = -1.322875656 Solving -3.5 + x = -1.322875656 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 = -1.322875656 + 3.5 Combine like terms: -3.5 + 3.5 = 0.0 0.0 + x = -1.322875656 + 3.5 x = -1.322875656 + 3.5 Combine like terms: -1.322875656 + 3.5 = 2.177124344 x = 2.177124344 Simplifying x = 2.177124344

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.822875656, 2.177124344}

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