a^2-15=4a

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Solution for a^2-15=4a equation:


Simplifying
a2 + -15 = 4a

Reorder the terms:
-15 + a2 = 4a

Solving
-15 + a2 = 4a

Solving for variable 'a'.

Reorder the terms:
-15 + -4a + a2 = 4a + -4a

Combine like terms: 4a + -4a = 0
-15 + -4a + a2 = 0

Begin completing the square.

Move the constant term to the right:

Add '15' to each side of the equation.
-15 + -4a + 15 + a2 = 0 + 15

Reorder the terms:
-15 + 15 + -4a + a2 = 0 + 15

Combine like terms: -15 + 15 = 0
0 + -4a + a2 = 0 + 15
-4a + a2 = 0 + 15

Combine like terms: 0 + 15 = 15
-4a + a2 = 15

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

Add '4' to each side of the equation.
-4a + 4 + a2 = 15 + 4

Reorder the terms:
4 + -4a + a2 = 15 + 4

Combine like terms: 15 + 4 = 19
4 + -4a + a2 = 19

Factor a perfect square on the left side:
(a + -2)(a + -2) = 19

Calculate the square root of the right side: 4.358898944

Break this problem into two subproblems by setting 
(a + -2) equal to 4.358898944 and -4.358898944.

Subproblem 1

a + -2 = 4.358898944 Simplifying a + -2 = 4.358898944 Reorder the terms: -2 + a = 4.358898944 Solving -2 + a = 4.358898944 Solving for variable 'a'. Move all terms containing a to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + a = 4.358898944 + 2 Combine like terms: -2 + 2 = 0 0 + a = 4.358898944 + 2 a = 4.358898944 + 2 Combine like terms: 4.358898944 + 2 = 6.358898944 a = 6.358898944 Simplifying a = 6.358898944

Subproblem 2

a + -2 = -4.358898944 Simplifying a + -2 = -4.358898944 Reorder the terms: -2 + a = -4.358898944 Solving -2 + a = -4.358898944 Solving for variable 'a'. Move all terms containing a to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + a = -4.358898944 + 2 Combine like terms: -2 + 2 = 0 0 + a = -4.358898944 + 2 a = -4.358898944 + 2 Combine like terms: -4.358898944 + 2 = -2.358898944 a = -2.358898944 Simplifying a = -2.358898944

Solution

The solution to the problem is based on the solutions from the subproblems. a = {6.358898944, -2.358898944}

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