7y^2+15y-9=0

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Solution for 7y^2+15y-9=0 equation:


Simplifying
7y2 + 15y + -9 = 0

Reorder the terms:
-9 + 15y + 7y2 = 0

Solving
-9 + 15y + 7y2 = 0

Solving for variable 'y'.

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

Divide each side by '7'.
-1.285714286 + 2.142857143y + y2 = 0

Move the constant term to the right:

Add '1.285714286' to each side of the equation.
-1.285714286 + 2.142857143y + 1.285714286 + y2 = 0 + 1.285714286

Reorder the terms:
-1.285714286 + 1.285714286 + 2.142857143y + y2 = 0 + 1.285714286

Combine like terms: -1.285714286 + 1.285714286 = 0.000000000
0.000000000 + 2.142857143y + y2 = 0 + 1.285714286
2.142857143y + y2 = 0 + 1.285714286

Combine like terms: 0 + 1.285714286 = 1.285714286
2.142857143y + y2 = 1.285714286

The y term is 2.142857143y.  Take half its coefficient (1.071428572).
Square it (1.147959185) and add it to both sides.

Add '1.147959185' to each side of the equation.
2.142857143y + 1.147959185 + y2 = 1.285714286 + 1.147959185

Reorder the terms:
1.147959185 + 2.142857143y + y2 = 1.285714286 + 1.147959185

Combine like terms: 1.285714286 + 1.147959185 = 2.433673471
1.147959185 + 2.142857143y + y2 = 2.433673471

Factor a perfect square on the left side:
(y + 1.071428572)(y + 1.071428572) = 2.433673471

Calculate the square root of the right side: 1.560023548

Break this problem into two subproblems by setting 
(y + 1.071428572) equal to 1.560023548 and -1.560023548.

Subproblem 1

y + 1.071428572 = 1.560023548 Simplifying y + 1.071428572 = 1.560023548 Reorder the terms: 1.071428572 + y = 1.560023548 Solving 1.071428572 + y = 1.560023548 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '-1.071428572' to each side of the equation. 1.071428572 + -1.071428572 + y = 1.560023548 + -1.071428572 Combine like terms: 1.071428572 + -1.071428572 = 0.000000000 0.000000000 + y = 1.560023548 + -1.071428572 y = 1.560023548 + -1.071428572 Combine like terms: 1.560023548 + -1.071428572 = 0.488594976 y = 0.488594976 Simplifying y = 0.488594976

Subproblem 2

y + 1.071428572 = -1.560023548 Simplifying y + 1.071428572 = -1.560023548 Reorder the terms: 1.071428572 + y = -1.560023548 Solving 1.071428572 + y = -1.560023548 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '-1.071428572' to each side of the equation. 1.071428572 + -1.071428572 + y = -1.560023548 + -1.071428572 Combine like terms: 1.071428572 + -1.071428572 = 0.000000000 0.000000000 + y = -1.560023548 + -1.071428572 y = -1.560023548 + -1.071428572 Combine like terms: -1.560023548 + -1.071428572 = -2.63145212 y = -2.63145212 Simplifying y = -2.63145212

Solution

The solution to the problem is based on the solutions from the subproblems. y = {0.488594976, -2.63145212}

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