6a^2-21=7a

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Solution for 6a^2-21=7a equation:


Simplifying
6a2 + -21 = 7a

Reorder the terms:
-21 + 6a2 = 7a

Solving
-21 + 6a2 = 7a

Solving for variable 'a'.

Reorder the terms:
-21 + -7a + 6a2 = 7a + -7a

Combine like terms: 7a + -7a = 0
-21 + -7a + 6a2 = 0

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

Divide each side by '6'.
-3.5 + -1.166666667a + a2 = 0

Move the constant term to the right:

Add '3.5' to each side of the equation.
-3.5 + -1.166666667a + 3.5 + a2 = 0 + 3.5

Reorder the terms:
-3.5 + 3.5 + -1.166666667a + a2 = 0 + 3.5

Combine like terms: -3.5 + 3.5 = 0.0
0.0 + -1.166666667a + a2 = 0 + 3.5
-1.166666667a + a2 = 0 + 3.5

Combine like terms: 0 + 3.5 = 3.5
-1.166666667a + a2 = 3.5

The a term is -1.166666667a.  Take half its coefficient (-0.5833333335).
Square it (0.3402777780) and add it to both sides.

Add '0.3402777780' to each side of the equation.
-1.166666667a + 0.3402777780 + a2 = 3.5 + 0.3402777780

Reorder the terms:
0.3402777780 + -1.166666667a + a2 = 3.5 + 0.3402777780

Combine like terms: 3.5 + 0.3402777780 = 3.840277778
0.3402777780 + -1.166666667a + a2 = 3.840277778

Factor a perfect square on the left side:
(a + -0.5833333335)(a + -0.5833333335) = 3.840277778

Calculate the square root of the right side: 1.959662669

Break this problem into two subproblems by setting 
(a + -0.5833333335) equal to 1.959662669 and -1.959662669.

Subproblem 1

a + -0.5833333335 = 1.959662669 Simplifying a + -0.5833333335 = 1.959662669 Reorder the terms: -0.5833333335 + a = 1.959662669 Solving -0.5833333335 + a = 1.959662669 Solving for variable 'a'. Move all terms containing a to the left, all other terms to the right. Add '0.5833333335' to each side of the equation. -0.5833333335 + 0.5833333335 + a = 1.959662669 + 0.5833333335 Combine like terms: -0.5833333335 + 0.5833333335 = 0.0000000000 0.0000000000 + a = 1.959662669 + 0.5833333335 a = 1.959662669 + 0.5833333335 Combine like terms: 1.959662669 + 0.5833333335 = 2.5429960025 a = 2.5429960025 Simplifying a = 2.5429960025

Subproblem 2

a + -0.5833333335 = -1.959662669 Simplifying a + -0.5833333335 = -1.959662669 Reorder the terms: -0.5833333335 + a = -1.959662669 Solving -0.5833333335 + a = -1.959662669 Solving for variable 'a'. Move all terms containing a to the left, all other terms to the right. Add '0.5833333335' to each side of the equation. -0.5833333335 + 0.5833333335 + a = -1.959662669 + 0.5833333335 Combine like terms: -0.5833333335 + 0.5833333335 = 0.0000000000 0.0000000000 + a = -1.959662669 + 0.5833333335 a = -1.959662669 + 0.5833333335 Combine like terms: -1.959662669 + 0.5833333335 = -1.3763293355 a = -1.3763293355 Simplifying a = -1.3763293355

Solution

The solution to the problem is based on the solutions from the subproblems. a = {2.5429960025, -1.3763293355}

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