a^2+8a=18

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Solution for a^2+8a=18 equation:


Simplifying
a2 + 8a = 18

Reorder the terms:
8a + a2 = 18

Solving
8a + a2 = 18

Solving for variable 'a'.

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

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

Begin completing the square.

Move the constant term to the right:

Add '18' to each side of the equation.
-18 + 8a + 18 + a2 = 0 + 18

Reorder the terms:
-18 + 18 + 8a + a2 = 0 + 18

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

Combine like terms: 0 + 18 = 18
8a + a2 = 18

The a term is 8a.  Take half its coefficient (4).
Square it (16) and add it to both sides.

Add '16' to each side of the equation.
8a + 16 + a2 = 18 + 16

Reorder the terms:
16 + 8a + a2 = 18 + 16

Combine like terms: 18 + 16 = 34
16 + 8a + a2 = 34

Factor a perfect square on the left side:
(a + 4)(a + 4) = 34

Calculate the square root of the right side: 5.830951895

Break this problem into two subproblems by setting 
(a + 4) equal to 5.830951895 and -5.830951895.

Subproblem 1

a + 4 = 5.830951895 Simplifying a + 4 = 5.830951895 Reorder the terms: 4 + a = 5.830951895 Solving 4 + a = 5.830951895 Solving for variable 'a'. Move all terms containing a to the left, all other terms to the right. Add '-4' to each side of the equation. 4 + -4 + a = 5.830951895 + -4 Combine like terms: 4 + -4 = 0 0 + a = 5.830951895 + -4 a = 5.830951895 + -4 Combine like terms: 5.830951895 + -4 = 1.830951895 a = 1.830951895 Simplifying a = 1.830951895

Subproblem 2

a + 4 = -5.830951895 Simplifying a + 4 = -5.830951895 Reorder the terms: 4 + a = -5.830951895 Solving 4 + a = -5.830951895 Solving for variable 'a'. Move all terms containing a to the left, all other terms to the right. Add '-4' to each side of the equation. 4 + -4 + a = -5.830951895 + -4 Combine like terms: 4 + -4 = 0 0 + a = -5.830951895 + -4 a = -5.830951895 + -4 Combine like terms: -5.830951895 + -4 = -9.830951895 a = -9.830951895 Simplifying a = -9.830951895

Solution

The solution to the problem is based on the solutions from the subproblems. a = {1.830951895, -9.830951895}

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