y^2+21y=19

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Solution for y^2+21y=19 equation:


Simplifying
y2 + 21y = 19

Reorder the terms:
21y + y2 = 19

Solving
21y + y2 = 19

Solving for variable 'y'.

Reorder the terms:
-19 + 21y + y2 = 19 + -19

Combine like terms: 19 + -19 = 0
-19 + 21y + y2 = 0

Begin completing the square.

Move the constant term to the right:

Add '19' to each side of the equation.
-19 + 21y + 19 + y2 = 0 + 19

Reorder the terms:
-19 + 19 + 21y + y2 = 0 + 19

Combine like terms: -19 + 19 = 0
0 + 21y + y2 = 0 + 19
21y + y2 = 0 + 19

Combine like terms: 0 + 19 = 19
21y + y2 = 19

The y term is 21y.  Take half its coefficient (10.5).
Square it (110.25) and add it to both sides.

Add '110.25' to each side of the equation.
21y + 110.25 + y2 = 19 + 110.25

Reorder the terms:
110.25 + 21y + y2 = 19 + 110.25

Combine like terms: 19 + 110.25 = 129.25
110.25 + 21y + y2 = 129.25

Factor a perfect square on the left side:
(y + 10.5)(y + 10.5) = 129.25

Calculate the square root of the right side: 11.368817001

Break this problem into two subproblems by setting 
(y + 10.5) equal to 11.368817001 and -11.368817001.

Subproblem 1

y + 10.5 = 11.368817001 Simplifying y + 10.5 = 11.368817001 Reorder the terms: 10.5 + y = 11.368817001 Solving 10.5 + y = 11.368817001 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '-10.5' to each side of the equation. 10.5 + -10.5 + y = 11.368817001 + -10.5 Combine like terms: 10.5 + -10.5 = 0.0 0.0 + y = 11.368817001 + -10.5 y = 11.368817001 + -10.5 Combine like terms: 11.368817001 + -10.5 = 0.868817001 y = 0.868817001 Simplifying y = 0.868817001

Subproblem 2

y + 10.5 = -11.368817001 Simplifying y + 10.5 = -11.368817001 Reorder the terms: 10.5 + y = -11.368817001 Solving 10.5 + y = -11.368817001 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '-10.5' to each side of the equation. 10.5 + -10.5 + y = -11.368817001 + -10.5 Combine like terms: 10.5 + -10.5 = 0.0 0.0 + y = -11.368817001 + -10.5 y = -11.368817001 + -10.5 Combine like terms: -11.368817001 + -10.5 = -21.868817001 y = -21.868817001 Simplifying y = -21.868817001

Solution

The solution to the problem is based on the solutions from the subproblems. y = {0.868817001, -21.868817001}

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