a(a-3)=120

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Solution for a(a-3)=120 equation:


Simplifying
a(a + -3) = 120

Reorder the terms:
a(-3 + a) = 120
(-3 * a + a * a) = 120
(-3a + a2) = 120

Solving
-3a + a2 = 120

Solving for variable 'a'.

Reorder the terms:
-120 + -3a + a2 = 120 + -120

Combine like terms: 120 + -120 = 0
-120 + -3a + a2 = 0

Begin completing the square.

Move the constant term to the right:

Add '120' to each side of the equation.
-120 + -3a + 120 + a2 = 0 + 120

Reorder the terms:
-120 + 120 + -3a + a2 = 0 + 120

Combine like terms: -120 + 120 = 0
0 + -3a + a2 = 0 + 120
-3a + a2 = 0 + 120

Combine like terms: 0 + 120 = 120
-3a + a2 = 120

The a term is -3a.  Take half its coefficient (-1.5).
Square it (2.25) and add it to both sides.

Add '2.25' to each side of the equation.
-3a + 2.25 + a2 = 120 + 2.25

Reorder the terms:
2.25 + -3a + a2 = 120 + 2.25

Combine like terms: 120 + 2.25 = 122.25
2.25 + -3a + a2 = 122.25

Factor a perfect square on the left side:
(a + -1.5)(a + -1.5) = 122.25

Calculate the square root of the right side: 11.056672194

Break this problem into two subproblems by setting 
(a + -1.5) equal to 11.056672194 and -11.056672194.

Subproblem 1

a + -1.5 = 11.056672194 Simplifying a + -1.5 = 11.056672194 Reorder the terms: -1.5 + a = 11.056672194 Solving -1.5 + a = 11.056672194 Solving for variable 'a'. Move all terms containing a to the left, all other terms to the right. Add '1.5' to each side of the equation. -1.5 + 1.5 + a = 11.056672194 + 1.5 Combine like terms: -1.5 + 1.5 = 0.0 0.0 + a = 11.056672194 + 1.5 a = 11.056672194 + 1.5 Combine like terms: 11.056672194 + 1.5 = 12.556672194 a = 12.556672194 Simplifying a = 12.556672194

Subproblem 2

a + -1.5 = -11.056672194 Simplifying a + -1.5 = -11.056672194 Reorder the terms: -1.5 + a = -11.056672194 Solving -1.5 + a = -11.056672194 Solving for variable 'a'. Move all terms containing a to the left, all other terms to the right. Add '1.5' to each side of the equation. -1.5 + 1.5 + a = -11.056672194 + 1.5 Combine like terms: -1.5 + 1.5 = 0.0 0.0 + a = -11.056672194 + 1.5 a = -11.056672194 + 1.5 Combine like terms: -11.056672194 + 1.5 = -9.556672194 a = -9.556672194 Simplifying a = -9.556672194

Solution

The solution to the problem is based on the solutions from the subproblems. a = {12.556672194, -9.556672194}

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