f^2+9f-4=0

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Solution for f^2+9f-4=0 equation:


Simplifying
f2 + 9f + -4 = 0

Reorder the terms:
-4 + 9f + f2 = 0

Solving
-4 + 9f + f2 = 0

Solving for variable 'f'.

Begin completing the square.

Move the constant term to the right:

Add '4' to each side of the equation.
-4 + 9f + 4 + f2 = 0 + 4

Reorder the terms:
-4 + 4 + 9f + f2 = 0 + 4

Combine like terms: -4 + 4 = 0
0 + 9f + f2 = 0 + 4
9f + f2 = 0 + 4

Combine like terms: 0 + 4 = 4
9f + f2 = 4

The f term is 9f.  Take half its coefficient (4.5).
Square it (20.25) and add it to both sides.

Add '20.25' to each side of the equation.
9f + 20.25 + f2 = 4 + 20.25

Reorder the terms:
20.25 + 9f + f2 = 4 + 20.25

Combine like terms: 4 + 20.25 = 24.25
20.25 + 9f + f2 = 24.25

Factor a perfect square on the left side:
(f + 4.5)(f + 4.5) = 24.25

Calculate the square root of the right side: 4.924428901

Break this problem into two subproblems by setting 
(f + 4.5) equal to 4.924428901 and -4.924428901.

Subproblem 1

f + 4.5 = 4.924428901 Simplifying f + 4.5 = 4.924428901 Reorder the terms: 4.5 + f = 4.924428901 Solving 4.5 + f = 4.924428901 Solving for variable 'f'. Move all terms containing f to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + f = 4.924428901 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + f = 4.924428901 + -4.5 f = 4.924428901 + -4.5 Combine like terms: 4.924428901 + -4.5 = 0.424428901 f = 0.424428901 Simplifying f = 0.424428901

Subproblem 2

f + 4.5 = -4.924428901 Simplifying f + 4.5 = -4.924428901 Reorder the terms: 4.5 + f = -4.924428901 Solving 4.5 + f = -4.924428901 Solving for variable 'f'. Move all terms containing f to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + f = -4.924428901 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + f = -4.924428901 + -4.5 f = -4.924428901 + -4.5 Combine like terms: -4.924428901 + -4.5 = -9.424428901 f = -9.424428901 Simplifying f = -9.424428901

Solution

The solution to the problem is based on the solutions from the subproblems. f = {0.424428901, -9.424428901}

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