7x^2+19x-21=0

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Solution for 7x^2+19x-21=0 equation:


Simplifying
7x2 + 19x + -21 = 0

Reorder the terms:
-21 + 19x + 7x2 = 0

Solving
-21 + 19x + 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 + 2.714285714x + x2 = 0

Move the constant term to the right:

Add '3' to each side of the equation.
-3 + 2.714285714x + 3 + x2 = 0 + 3

Reorder the terms:
-3 + 3 + 2.714285714x + x2 = 0 + 3

Combine like terms: -3 + 3 = 0
0 + 2.714285714x + x2 = 0 + 3
2.714285714x + x2 = 0 + 3

Combine like terms: 0 + 3 = 3
2.714285714x + x2 = 3

The x term is 2.714285714x.  Take half its coefficient (1.357142857).
Square it (1.841836734) and add it to both sides.

Add '1.841836734' to each side of the equation.
2.714285714x + 1.841836734 + x2 = 3 + 1.841836734

Reorder the terms:
1.841836734 + 2.714285714x + x2 = 3 + 1.841836734

Combine like terms: 3 + 1.841836734 = 4.841836734
1.841836734 + 2.714285714x + x2 = 4.841836734

Factor a perfect square on the left side:
(x + 1.357142857)(x + 1.357142857) = 4.841836734

Calculate the square root of the right side: 2.2004174

Break this problem into two subproblems by setting 
(x + 1.357142857) equal to 2.2004174 and -2.2004174.

Subproblem 1

x + 1.357142857 = 2.2004174 Simplifying x + 1.357142857 = 2.2004174 Reorder the terms: 1.357142857 + x = 2.2004174 Solving 1.357142857 + x = 2.2004174 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.357142857' to each side of the equation. 1.357142857 + -1.357142857 + x = 2.2004174 + -1.357142857 Combine like terms: 1.357142857 + -1.357142857 = 0.000000000 0.000000000 + x = 2.2004174 + -1.357142857 x = 2.2004174 + -1.357142857 Combine like terms: 2.2004174 + -1.357142857 = 0.843274543 x = 0.843274543 Simplifying x = 0.843274543

Subproblem 2

x + 1.357142857 = -2.2004174 Simplifying x + 1.357142857 = -2.2004174 Reorder the terms: 1.357142857 + x = -2.2004174 Solving 1.357142857 + x = -2.2004174 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.357142857' to each side of the equation. 1.357142857 + -1.357142857 + x = -2.2004174 + -1.357142857 Combine like terms: 1.357142857 + -1.357142857 = 0.000000000 0.000000000 + x = -2.2004174 + -1.357142857 x = -2.2004174 + -1.357142857 Combine like terms: -2.2004174 + -1.357142857 = -3.557560257 x = -3.557560257 Simplifying x = -3.557560257

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.843274543, -3.557560257}

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