21y-(y(y-1))=4

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Solution for 21y-(y(y-1))=4 equation:


Simplifying
21y + -1(y(y + -1)) = 4

Reorder the terms:
21y + -1(y(-1 + y)) = 4
21y + -1((-1 * y + y * y)) = 4
21y + -1((-1y + y2)) = 4
21y + (-1y * -1 + y2 * -1) = 4
21y + (1y + -1y2) = 4

Combine like terms: 21y + 1y = 22y
22y + -1y2 = 4

Solving
22y + -1y2 = 4

Solving for variable 'y'.

Reorder the terms:
-4 + 22y + -1y2 = 4 + -4

Combine like terms: 4 + -4 = 0
-4 + 22y + -1y2 = 0

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
4 + -22y + y2 = 0

Move the constant term to the right:

Add '-4' to each side of the equation.
4 + -22y + -4 + y2 = 0 + -4

Reorder the terms:
4 + -4 + -22y + y2 = 0 + -4

Combine like terms: 4 + -4 = 0
0 + -22y + y2 = 0 + -4
-22y + y2 = 0 + -4

Combine like terms: 0 + -4 = -4
-22y + y2 = -4

The y term is -22y.  Take half its coefficient (-11).
Square it (121) and add it to both sides.

Add '121' to each side of the equation.
-22y + 121 + y2 = -4 + 121

Reorder the terms:
121 + -22y + y2 = -4 + 121

Combine like terms: -4 + 121 = 117
121 + -22y + y2 = 117

Factor a perfect square on the left side:
(y + -11)(y + -11) = 117

Calculate the square root of the right side: 10.816653826

Break this problem into two subproblems by setting 
(y + -11) equal to 10.816653826 and -10.816653826.

Subproblem 1

y + -11 = 10.816653826 Simplifying y + -11 = 10.816653826 Reorder the terms: -11 + y = 10.816653826 Solving -11 + y = 10.816653826 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '11' to each side of the equation. -11 + 11 + y = 10.816653826 + 11 Combine like terms: -11 + 11 = 0 0 + y = 10.816653826 + 11 y = 10.816653826 + 11 Combine like terms: 10.816653826 + 11 = 21.816653826 y = 21.816653826 Simplifying y = 21.816653826

Subproblem 2

y + -11 = -10.816653826 Simplifying y + -11 = -10.816653826 Reorder the terms: -11 + y = -10.816653826 Solving -11 + y = -10.816653826 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '11' to each side of the equation. -11 + 11 + y = -10.816653826 + 11 Combine like terms: -11 + 11 = 0 0 + y = -10.816653826 + 11 y = -10.816653826 + 11 Combine like terms: -10.816653826 + 11 = 0.183346174 y = 0.183346174 Simplifying y = 0.183346174

Solution

The solution to the problem is based on the solutions from the subproblems. y = {21.816653826, 0.183346174}

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