81-18y+y^2=18

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Solution for 81-18y+y^2=18 equation:


Simplifying
81 + -18y + y2 = 18

Solving
81 + -18y + y2 = 18

Solving for variable 'y'.

Reorder the terms:
81 + -18 + -18y + y2 = 18 + -18

Combine like terms: 81 + -18 = 63
63 + -18y + y2 = 18 + -18

Combine like terms: 18 + -18 = 0
63 + -18y + y2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-63' to each side of the equation.
63 + -18y + -63 + y2 = 0 + -63

Reorder the terms:
63 + -63 + -18y + y2 = 0 + -63

Combine like terms: 63 + -63 = 0
0 + -18y + y2 = 0 + -63
-18y + y2 = 0 + -63

Combine like terms: 0 + -63 = -63
-18y + y2 = -63

The y term is -18y.  Take half its coefficient (-9).
Square it (81) and add it to both sides.

Add '81' to each side of the equation.
-18y + 81 + y2 = -63 + 81

Reorder the terms:
81 + -18y + y2 = -63 + 81

Combine like terms: -63 + 81 = 18
81 + -18y + y2 = 18

Factor a perfect square on the left side:
(y + -9)(y + -9) = 18

Calculate the square root of the right side: 4.242640687

Break this problem into two subproblems by setting 
(y + -9) equal to 4.242640687 and -4.242640687.

Subproblem 1

y + -9 = 4.242640687 Simplifying y + -9 = 4.242640687 Reorder the terms: -9 + y = 4.242640687 Solving -9 + y = 4.242640687 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '9' to each side of the equation. -9 + 9 + y = 4.242640687 + 9 Combine like terms: -9 + 9 = 0 0 + y = 4.242640687 + 9 y = 4.242640687 + 9 Combine like terms: 4.242640687 + 9 = 13.242640687 y = 13.242640687 Simplifying y = 13.242640687

Subproblem 2

y + -9 = -4.242640687 Simplifying y + -9 = -4.242640687 Reorder the terms: -9 + y = -4.242640687 Solving -9 + y = -4.242640687 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '9' to each side of the equation. -9 + 9 + y = -4.242640687 + 9 Combine like terms: -9 + 9 = 0 0 + y = -4.242640687 + 9 y = -4.242640687 + 9 Combine like terms: -4.242640687 + 9 = 4.757359313 y = 4.757359313 Simplifying y = 4.757359313

Solution

The solution to the problem is based on the solutions from the subproblems. y = {13.242640687, 4.757359313}

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