7r^2+11r-9=0

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Solution for 7r^2+11r-9=0 equation:


Simplifying
7r2 + 11r + -9 = 0

Reorder the terms:
-9 + 11r + 7r2 = 0

Solving
-9 + 11r + 7r2 = 0

Solving for variable 'r'.

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

Divide each side by '7'.
-1.285714286 + 1.571428571r + r2 = 0

Move the constant term to the right:

Add '1.285714286' to each side of the equation.
-1.285714286 + 1.571428571r + 1.285714286 + r2 = 0 + 1.285714286

Reorder the terms:
-1.285714286 + 1.285714286 + 1.571428571r + r2 = 0 + 1.285714286

Combine like terms: -1.285714286 + 1.285714286 = 0.000000000
0.000000000 + 1.571428571r + r2 = 0 + 1.285714286
1.571428571r + r2 = 0 + 1.285714286

Combine like terms: 0 + 1.285714286 = 1.285714286
1.571428571r + r2 = 1.285714286

The r term is 1.571428571r.  Take half its coefficient (0.7857142855).
Square it (0.6173469384) and add it to both sides.

Add '0.6173469384' to each side of the equation.
1.571428571r + 0.6173469384 + r2 = 1.285714286 + 0.6173469384

Reorder the terms:
0.6173469384 + 1.571428571r + r2 = 1.285714286 + 0.6173469384

Combine like terms: 1.285714286 + 0.6173469384 = 1.9030612244
0.6173469384 + 1.571428571r + r2 = 1.9030612244

Factor a perfect square on the left side:
(r + 0.7857142855)(r + 0.7857142855) = 1.9030612244

Calculate the square root of the right side: 1.379514851

Break this problem into two subproblems by setting 
(r + 0.7857142855) equal to 1.379514851 and -1.379514851.

Subproblem 1

r + 0.7857142855 = 1.379514851 Simplifying r + 0.7857142855 = 1.379514851 Reorder the terms: 0.7857142855 + r = 1.379514851 Solving 0.7857142855 + r = 1.379514851 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-0.7857142855' to each side of the equation. 0.7857142855 + -0.7857142855 + r = 1.379514851 + -0.7857142855 Combine like terms: 0.7857142855 + -0.7857142855 = 0.0000000000 0.0000000000 + r = 1.379514851 + -0.7857142855 r = 1.379514851 + -0.7857142855 Combine like terms: 1.379514851 + -0.7857142855 = 0.5938005655 r = 0.5938005655 Simplifying r = 0.5938005655

Subproblem 2

r + 0.7857142855 = -1.379514851 Simplifying r + 0.7857142855 = -1.379514851 Reorder the terms: 0.7857142855 + r = -1.379514851 Solving 0.7857142855 + r = -1.379514851 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '-0.7857142855' to each side of the equation. 0.7857142855 + -0.7857142855 + r = -1.379514851 + -0.7857142855 Combine like terms: 0.7857142855 + -0.7857142855 = 0.0000000000 0.0000000000 + r = -1.379514851 + -0.7857142855 r = -1.379514851 + -0.7857142855 Combine like terms: -1.379514851 + -0.7857142855 = -2.1652291365 r = -2.1652291365 Simplifying r = -2.1652291365

Solution

The solution to the problem is based on the solutions from the subproblems. r = {0.5938005655, -2.1652291365}

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