t^2-21t-126=0

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Solution for t^2-21t-126=0 equation:


Simplifying
t2 + -21t + -126 = 0

Reorder the terms:
-126 + -21t + t2 = 0

Solving
-126 + -21t + t2 = 0

Solving for variable 't'.

Begin completing the square.

Move the constant term to the right:

Add '126' to each side of the equation.
-126 + -21t + 126 + t2 = 0 + 126

Reorder the terms:
-126 + 126 + -21t + t2 = 0 + 126

Combine like terms: -126 + 126 = 0
0 + -21t + t2 = 0 + 126
-21t + t2 = 0 + 126

Combine like terms: 0 + 126 = 126
-21t + t2 = 126

The t term is -21t.  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.
-21t + 110.25 + t2 = 126 + 110.25

Reorder the terms:
110.25 + -21t + t2 = 126 + 110.25

Combine like terms: 126 + 110.25 = 236.25
110.25 + -21t + t2 = 236.25

Factor a perfect square on the left side:
(t + -10.5)(t + -10.5) = 236.25

Calculate the square root of the right side: 15.370426149

Break this problem into two subproblems by setting 
(t + -10.5) equal to 15.370426149 and -15.370426149.

Subproblem 1

t + -10.5 = 15.370426149 Simplifying t + -10.5 = 15.370426149 Reorder the terms: -10.5 + t = 15.370426149 Solving -10.5 + t = 15.370426149 Solving for variable 't'. Move all terms containing t to the left, all other terms to the right. Add '10.5' to each side of the equation. -10.5 + 10.5 + t = 15.370426149 + 10.5 Combine like terms: -10.5 + 10.5 = 0.0 0.0 + t = 15.370426149 + 10.5 t = 15.370426149 + 10.5 Combine like terms: 15.370426149 + 10.5 = 25.870426149 t = 25.870426149 Simplifying t = 25.870426149

Subproblem 2

t + -10.5 = -15.370426149 Simplifying t + -10.5 = -15.370426149 Reorder the terms: -10.5 + t = -15.370426149 Solving -10.5 + t = -15.370426149 Solving for variable 't'. Move all terms containing t to the left, all other terms to the right. Add '10.5' to each side of the equation. -10.5 + 10.5 + t = -15.370426149 + 10.5 Combine like terms: -10.5 + 10.5 = 0.0 0.0 + t = -15.370426149 + 10.5 t = -15.370426149 + 10.5 Combine like terms: -15.370426149 + 10.5 = -4.870426149 t = -4.870426149 Simplifying t = -4.870426149

Solution

The solution to the problem is based on the solutions from the subproblems. t = {25.870426149, -4.870426149}

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