9a^2-17a-21=8a^2+a

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Solution for 9a^2-17a-21=8a^2+a equation:


Simplifying
9a2 + -17a + -21 = 8a2 + a

Reorder the terms:
-21 + -17a + 9a2 = 8a2 + a

Reorder the terms:
-21 + -17a + 9a2 = a + 8a2

Solving
-21 + -17a + 9a2 = a + 8a2

Solving for variable 'a'.

Reorder the terms:
-21 + -17a + -1a + 9a2 + -8a2 = a + 8a2 + -1a + -8a2

Combine like terms: -17a + -1a = -18a
-21 + -18a + 9a2 + -8a2 = a + 8a2 + -1a + -8a2

Combine like terms: 9a2 + -8a2 = 1a2
-21 + -18a + 1a2 = a + 8a2 + -1a + -8a2

Reorder the terms:
-21 + -18a + 1a2 = a + -1a + 8a2 + -8a2

Combine like terms: a + -1a = 0
-21 + -18a + 1a2 = 0 + 8a2 + -8a2
-21 + -18a + 1a2 = 8a2 + -8a2

Combine like terms: 8a2 + -8a2 = 0
-21 + -18a + 1a2 = 0

Begin completing the square.

Move the constant term to the right:

Add '21' to each side of the equation.
-21 + -18a + 21 + a2 = 0 + 21

Reorder the terms:
-21 + 21 + -18a + a2 = 0 + 21

Combine like terms: -21 + 21 = 0
0 + -18a + a2 = 0 + 21
-18a + a2 = 0 + 21

Combine like terms: 0 + 21 = 21
-18a + a2 = 21

The a term is -18a.  Take half its coefficient (-9).
Square it (81) and add it to both sides.

Add '81' to each side of the equation.
-18a + 81 + a2 = 21 + 81

Reorder the terms:
81 + -18a + a2 = 21 + 81

Combine like terms: 21 + 81 = 102
81 + -18a + a2 = 102

Factor a perfect square on the left side:
(a + -9)(a + -9) = 102

Calculate the square root of the right side: 10.099504938

Break this problem into two subproblems by setting 
(a + -9) equal to 10.099504938 and -10.099504938.

Subproblem 1

a + -9 = 10.099504938 Simplifying a + -9 = 10.099504938 Reorder the terms: -9 + a = 10.099504938 Solving -9 + a = 10.099504938 Solving for variable 'a'. Move all terms containing a to the left, all other terms to the right. Add '9' to each side of the equation. -9 + 9 + a = 10.099504938 + 9 Combine like terms: -9 + 9 = 0 0 + a = 10.099504938 + 9 a = 10.099504938 + 9 Combine like terms: 10.099504938 + 9 = 19.099504938 a = 19.099504938 Simplifying a = 19.099504938

Subproblem 2

a + -9 = -10.099504938 Simplifying a + -9 = -10.099504938 Reorder the terms: -9 + a = -10.099504938 Solving -9 + a = -10.099504938 Solving for variable 'a'. Move all terms containing a to the left, all other terms to the right. Add '9' to each side of the equation. -9 + 9 + a = -10.099504938 + 9 Combine like terms: -9 + 9 = 0 0 + a = -10.099504938 + 9 a = -10.099504938 + 9 Combine like terms: -10.099504938 + 9 = -1.099504938 a = -1.099504938 Simplifying a = -1.099504938

Solution

The solution to the problem is based on the solutions from the subproblems. a = {19.099504938, -1.099504938}

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