7y^2+18y-8=0

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Solution for 7y^2+18y-8=0 equation:


Simplifying
7y2 + 18y + -8 = 0

Reorder the terms:
-8 + 18y + 7y2 = 0

Solving
-8 + 18y + 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'.
-1.142857143 + 2.571428571y + y2 = 0

Move the constant term to the right:

Add '1.142857143' to each side of the equation.
-1.142857143 + 2.571428571y + 1.142857143 + y2 = 0 + 1.142857143

Reorder the terms:
-1.142857143 + 1.142857143 + 2.571428571y + y2 = 0 + 1.142857143

Combine like terms: -1.142857143 + 1.142857143 = 0.000000000
0.000000000 + 2.571428571y + y2 = 0 + 1.142857143
2.571428571y + y2 = 0 + 1.142857143

Combine like terms: 0 + 1.142857143 = 1.142857143
2.571428571y + y2 = 1.142857143

The y term is 2.571428571y.  Take half its coefficient (1.285714286).
Square it (1.653061225) and add it to both sides.

Add '1.653061225' to each side of the equation.
2.571428571y + 1.653061225 + y2 = 1.142857143 + 1.653061225

Reorder the terms:
1.653061225 + 2.571428571y + y2 = 1.142857143 + 1.653061225

Combine like terms: 1.142857143 + 1.653061225 = 2.795918368
1.653061225 + 2.571428571y + y2 = 2.795918368

Factor a perfect square on the left side:
(y + 1.285714286)(y + 1.285714286) = 2.795918368

Calculate the square root of the right side: 1.672099987

Break this problem into two subproblems by setting 
(y + 1.285714286) equal to 1.672099987 and -1.672099987.

Subproblem 1

y + 1.285714286 = 1.672099987 Simplifying y + 1.285714286 = 1.672099987 Reorder the terms: 1.285714286 + y = 1.672099987 Solving 1.285714286 + y = 1.672099987 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '-1.285714286' to each side of the equation. 1.285714286 + -1.285714286 + y = 1.672099987 + -1.285714286 Combine like terms: 1.285714286 + -1.285714286 = 0.000000000 0.000000000 + y = 1.672099987 + -1.285714286 y = 1.672099987 + -1.285714286 Combine like terms: 1.672099987 + -1.285714286 = 0.386385701 y = 0.386385701 Simplifying y = 0.386385701

Subproblem 2

y + 1.285714286 = -1.672099987 Simplifying y + 1.285714286 = -1.672099987 Reorder the terms: 1.285714286 + y = -1.672099987 Solving 1.285714286 + y = -1.672099987 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '-1.285714286' to each side of the equation. 1.285714286 + -1.285714286 + y = -1.672099987 + -1.285714286 Combine like terms: 1.285714286 + -1.285714286 = 0.000000000 0.000000000 + y = -1.672099987 + -1.285714286 y = -1.672099987 + -1.285714286 Combine like terms: -1.672099987 + -1.285714286 = -2.957814273 y = -2.957814273 Simplifying y = -2.957814273

Solution

The solution to the problem is based on the solutions from the subproblems. y = {0.386385701, -2.957814273}

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