21=t^2-t

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Solution for 21=t^2-t equation:


Simplifying
21 = t2 + -1t

Reorder the terms:
21 = -1t + t2

Solving
21 = -1t + t2

Solving for variable 't'.

Reorder the terms:
21 + t + -1t2 = -1t + t + t2 + -1t2

Combine like terms: -1t + t = 0
21 + t + -1t2 = 0 + t2 + -1t2
21 + t + -1t2 = t2 + -1t2

Combine like terms: t2 + -1t2 = 0
21 + t + -1t2 = 0

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

Divide each side by '-1'.
-21 + -1t + t2 = 0

Move the constant term to the right:

Add '21' to each side of the equation.
-21 + -1t + 21 + t2 = 0 + 21

Reorder the terms:
-21 + 21 + -1t + t2 = 0 + 21

Combine like terms: -21 + 21 = 0
0 + -1t + t2 = 0 + 21
-1t + t2 = 0 + 21

Combine like terms: 0 + 21 = 21
-1t + t2 = 21

The t term is t.  Take half its coefficient (0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
-1t + 0.25 + t2 = 21 + 0.25

Reorder the terms:
0.25 + -1t + t2 = 21 + 0.25

Combine like terms: 21 + 0.25 = 21.25
0.25 + -1t + t2 = 21.25

Factor a perfect square on the left side:
(t + 0.5)(t + 0.5) = 21.25

Calculate the square root of the right side: 4.609772229

Break this problem into two subproblems by setting 
(t + 0.5) equal to 4.609772229 and -4.609772229.

Subproblem 1

t + 0.5 = 4.609772229 Simplifying t + 0.5 = 4.609772229 Reorder the terms: 0.5 + t = 4.609772229 Solving 0.5 + t = 4.609772229 Solving for variable 't'. Move all terms containing t to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + t = 4.609772229 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + t = 4.609772229 + -0.5 t = 4.609772229 + -0.5 Combine like terms: 4.609772229 + -0.5 = 4.109772229 t = 4.109772229 Simplifying t = 4.109772229

Subproblem 2

t + 0.5 = -4.609772229 Simplifying t + 0.5 = -4.609772229 Reorder the terms: 0.5 + t = -4.609772229 Solving 0.5 + t = -4.609772229 Solving for variable 't'. Move all terms containing t to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + t = -4.609772229 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + t = -4.609772229 + -0.5 t = -4.609772229 + -0.5 Combine like terms: -4.609772229 + -0.5 = -5.109772229 t = -5.109772229 Simplifying t = -5.109772229

Solution

The solution to the problem is based on the solutions from the subproblems. t = {4.109772229, -5.109772229}

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