7f^2+f-9=0

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Solution for 7f^2+f-9=0 equation:


Simplifying
7f2 + f + -9 = 0

Reorder the terms:
-9 + f + 7f2 = 0

Solving
-9 + f + 7f2 = 0

Solving for variable 'f'.

Begin completing the square.  Divide all terms by
7 the coefficient of the squared term: 

Divide each side by '7'.
-1.285714286 + 0.1428571429f + f2 = 0

Move the constant term to the right:

Add '1.285714286' to each side of the equation.
-1.285714286 + 0.1428571429f + 1.285714286 + f2 = 0 + 1.285714286

Reorder the terms:
-1.285714286 + 1.285714286 + 0.1428571429f + f2 = 0 + 1.285714286

Combine like terms: -1.285714286 + 1.285714286 = 0.000000000
0.000000000 + 0.1428571429f + f2 = 0 + 1.285714286
0.1428571429f + f2 = 0 + 1.285714286

Combine like terms: 0 + 1.285714286 = 1.285714286
0.1428571429f + f2 = 1.285714286

The f term is f.  Take half its coefficient (0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
0.1428571429f + 0.25 + f2 = 1.285714286 + 0.25

Reorder the terms:
0.25 + 0.1428571429f + f2 = 1.285714286 + 0.25

Combine like terms: 1.285714286 + 0.25 = 1.535714286
0.25 + 0.1428571429f + f2 = 1.535714286

Factor a perfect square on the left side:
(f + 0.5)(f + 0.5) = 1.535714286

Calculate the square root of the right side: 1.239239398

Break this problem into two subproblems by setting 
(f + 0.5) equal to 1.239239398 and -1.239239398.

Subproblem 1

f + 0.5 = 1.239239398 Simplifying f + 0.5 = 1.239239398 Reorder the terms: 0.5 + f = 1.239239398 Solving 0.5 + f = 1.239239398 Solving for variable 'f'. Move all terms containing f to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + f = 1.239239398 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + f = 1.239239398 + -0.5 f = 1.239239398 + -0.5 Combine like terms: 1.239239398 + -0.5 = 0.739239398 f = 0.739239398 Simplifying f = 0.739239398

Subproblem 2

f + 0.5 = -1.239239398 Simplifying f + 0.5 = -1.239239398 Reorder the terms: 0.5 + f = -1.239239398 Solving 0.5 + f = -1.239239398 Solving for variable 'f'. Move all terms containing f to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + f = -1.239239398 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + f = -1.239239398 + -0.5 f = -1.239239398 + -0.5 Combine like terms: -1.239239398 + -0.5 = -1.739239398 f = -1.739239398 Simplifying f = -1.739239398

Solution

The solution to the problem is based on the solutions from the subproblems. f = {0.739239398, -1.739239398}

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