7y^2+9y-18=0

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Solution for 7y^2+9y-18=0 equation:


Simplifying
7y2 + 9y + -18 = 0

Reorder the terms:
-18 + 9y + 7y2 = 0

Solving
-18 + 9y + 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'.
-2.571428571 + 1.285714286y + y2 = 0

Move the constant term to the right:

Add '2.571428571' to each side of the equation.
-2.571428571 + 1.285714286y + 2.571428571 + y2 = 0 + 2.571428571

Reorder the terms:
-2.571428571 + 2.571428571 + 1.285714286y + y2 = 0 + 2.571428571

Combine like terms: -2.571428571 + 2.571428571 = 0.000000000
0.000000000 + 1.285714286y + y2 = 0 + 2.571428571
1.285714286y + y2 = 0 + 2.571428571

Combine like terms: 0 + 2.571428571 = 2.571428571
1.285714286y + y2 = 2.571428571

The y term is 1.285714286y.  Take half its coefficient (0.642857143).
Square it (0.4132653063) and add it to both sides.

Add '0.4132653063' to each side of the equation.
1.285714286y + 0.4132653063 + y2 = 2.571428571 + 0.4132653063

Reorder the terms:
0.4132653063 + 1.285714286y + y2 = 2.571428571 + 0.4132653063

Combine like terms: 2.571428571 + 0.4132653063 = 2.9846938773
0.4132653063 + 1.285714286y + y2 = 2.9846938773

Factor a perfect square on the left side:
(y + 0.642857143)(y + 0.642857143) = 2.9846938773

Calculate the square root of the right side: 1.72762666

Break this problem into two subproblems by setting 
(y + 0.642857143) equal to 1.72762666 and -1.72762666.

Subproblem 1

y + 0.642857143 = 1.72762666 Simplifying y + 0.642857143 = 1.72762666 Reorder the terms: 0.642857143 + y = 1.72762666 Solving 0.642857143 + y = 1.72762666 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '-0.642857143' to each side of the equation. 0.642857143 + -0.642857143 + y = 1.72762666 + -0.642857143 Combine like terms: 0.642857143 + -0.642857143 = 0.000000000 0.000000000 + y = 1.72762666 + -0.642857143 y = 1.72762666 + -0.642857143 Combine like terms: 1.72762666 + -0.642857143 = 1.084769517 y = 1.084769517 Simplifying y = 1.084769517

Subproblem 2

y + 0.642857143 = -1.72762666 Simplifying y + 0.642857143 = -1.72762666 Reorder the terms: 0.642857143 + y = -1.72762666 Solving 0.642857143 + y = -1.72762666 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '-0.642857143' to each side of the equation. 0.642857143 + -0.642857143 + y = -1.72762666 + -0.642857143 Combine like terms: 0.642857143 + -0.642857143 = 0.000000000 0.000000000 + y = -1.72762666 + -0.642857143 y = -1.72762666 + -0.642857143 Combine like terms: -1.72762666 + -0.642857143 = -2.370483803 y = -2.370483803 Simplifying y = -2.370483803

Solution

The solution to the problem is based on the solutions from the subproblems. y = {1.084769517, -2.370483803}

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