8q^2-21=7q^2-4q+15

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Solution for 8q^2-21=7q^2-4q+15 equation:


Simplifying
8q2 + -21 = 7q2 + -4q + 15

Reorder the terms:
-21 + 8q2 = 7q2 + -4q + 15

Reorder the terms:
-21 + 8q2 = 15 + -4q + 7q2

Solving
-21 + 8q2 = 15 + -4q + 7q2

Solving for variable 'q'.

Reorder the terms:
-21 + -15 + 4q + 8q2 + -7q2 = 15 + -4q + 7q2 + -15 + 4q + -7q2

Combine like terms: -21 + -15 = -36
-36 + 4q + 8q2 + -7q2 = 15 + -4q + 7q2 + -15 + 4q + -7q2

Combine like terms: 8q2 + -7q2 = 1q2
-36 + 4q + 1q2 = 15 + -4q + 7q2 + -15 + 4q + -7q2

Reorder the terms:
-36 + 4q + 1q2 = 15 + -15 + -4q + 4q + 7q2 + -7q2

Combine like terms: 15 + -15 = 0
-36 + 4q + 1q2 = 0 + -4q + 4q + 7q2 + -7q2
-36 + 4q + 1q2 = -4q + 4q + 7q2 + -7q2

Combine like terms: -4q + 4q = 0
-36 + 4q + 1q2 = 0 + 7q2 + -7q2
-36 + 4q + 1q2 = 7q2 + -7q2

Combine like terms: 7q2 + -7q2 = 0
-36 + 4q + 1q2 = 0

Begin completing the square.

Move the constant term to the right:

Add '36' to each side of the equation.
-36 + 4q + 36 + q2 = 0 + 36

Reorder the terms:
-36 + 36 + 4q + q2 = 0 + 36

Combine like terms: -36 + 36 = 0
0 + 4q + q2 = 0 + 36
4q + q2 = 0 + 36

Combine like terms: 0 + 36 = 36
4q + q2 = 36

The q term is 4q.  Take half its coefficient (2).
Square it (4) and add it to both sides.

Add '4' to each side of the equation.
4q + 4 + q2 = 36 + 4

Reorder the terms:
4 + 4q + q2 = 36 + 4

Combine like terms: 36 + 4 = 40
4 + 4q + q2 = 40

Factor a perfect square on the left side:
(q + 2)(q + 2) = 40

Calculate the square root of the right side: 6.32455532

Break this problem into two subproblems by setting 
(q + 2) equal to 6.32455532 and -6.32455532.

Subproblem 1

q + 2 = 6.32455532 Simplifying q + 2 = 6.32455532 Reorder the terms: 2 + q = 6.32455532 Solving 2 + q = 6.32455532 Solving for variable 'q'. Move all terms containing q to the left, all other terms to the right. Add '-2' to each side of the equation. 2 + -2 + q = 6.32455532 + -2 Combine like terms: 2 + -2 = 0 0 + q = 6.32455532 + -2 q = 6.32455532 + -2 Combine like terms: 6.32455532 + -2 = 4.32455532 q = 4.32455532 Simplifying q = 4.32455532

Subproblem 2

q + 2 = -6.32455532 Simplifying q + 2 = -6.32455532 Reorder the terms: 2 + q = -6.32455532 Solving 2 + q = -6.32455532 Solving for variable 'q'. Move all terms containing q to the left, all other terms to the right. Add '-2' to each side of the equation. 2 + -2 + q = -6.32455532 + -2 Combine like terms: 2 + -2 = 0 0 + q = -6.32455532 + -2 q = -6.32455532 + -2 Combine like terms: -6.32455532 + -2 = -8.32455532 q = -8.32455532 Simplifying q = -8.32455532

Solution

The solution to the problem is based on the solutions from the subproblems. q = {4.32455532, -8.32455532}

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