7x^2+16x-21=0

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Solution for 7x^2+16x-21=0 equation:


Simplifying
7x2 + 16x + -21 = 0

Reorder the terms:
-21 + 16x + 7x2 = 0

Solving
-21 + 16x + 7x2 = 0

Solving for variable 'x'.

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

Divide each side by '7'.
-3 + 2.285714286x + x2 = 0

Move the constant term to the right:

Add '3' to each side of the equation.
-3 + 2.285714286x + 3 + x2 = 0 + 3

Reorder the terms:
-3 + 3 + 2.285714286x + x2 = 0 + 3

Combine like terms: -3 + 3 = 0
0 + 2.285714286x + x2 = 0 + 3
2.285714286x + x2 = 0 + 3

Combine like terms: 0 + 3 = 3
2.285714286x + x2 = 3

The x term is 2.285714286x.  Take half its coefficient (1.142857143).
Square it (1.306122449) and add it to both sides.

Add '1.306122449' to each side of the equation.
2.285714286x + 1.306122449 + x2 = 3 + 1.306122449

Reorder the terms:
1.306122449 + 2.285714286x + x2 = 3 + 1.306122449

Combine like terms: 3 + 1.306122449 = 4.306122449
1.306122449 + 2.285714286x + x2 = 4.306122449

Factor a perfect square on the left side:
(x + 1.142857143)(x + 1.142857143) = 4.306122449

Calculate the square root of the right side: 2.075119864

Break this problem into two subproblems by setting 
(x + 1.142857143) equal to 2.075119864 and -2.075119864.

Subproblem 1

x + 1.142857143 = 2.075119864 Simplifying x + 1.142857143 = 2.075119864 Reorder the terms: 1.142857143 + x = 2.075119864 Solving 1.142857143 + x = 2.075119864 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.142857143' to each side of the equation. 1.142857143 + -1.142857143 + x = 2.075119864 + -1.142857143 Combine like terms: 1.142857143 + -1.142857143 = 0.000000000 0.000000000 + x = 2.075119864 + -1.142857143 x = 2.075119864 + -1.142857143 Combine like terms: 2.075119864 + -1.142857143 = 0.932262721 x = 0.932262721 Simplifying x = 0.932262721

Subproblem 2

x + 1.142857143 = -2.075119864 Simplifying x + 1.142857143 = -2.075119864 Reorder the terms: 1.142857143 + x = -2.075119864 Solving 1.142857143 + x = -2.075119864 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.142857143' to each side of the equation. 1.142857143 + -1.142857143 + x = -2.075119864 + -1.142857143 Combine like terms: 1.142857143 + -1.142857143 = 0.000000000 0.000000000 + x = -2.075119864 + -1.142857143 x = -2.075119864 + -1.142857143 Combine like terms: -2.075119864 + -1.142857143 = -3.217977007 x = -3.217977007 Simplifying x = -3.217977007

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.932262721, -3.217977007}

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