t(t-40)=21

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Solution for t(t-40)=21 equation:


Simplifying
t(t + -40) = 21

Reorder the terms:
t(-40 + t) = 21
(-40 * t + t * t) = 21
(-40t + t2) = 21

Solving
-40t + t2 = 21

Solving for variable 't'.

Reorder the terms:
-21 + -40t + t2 = 21 + -21

Combine like terms: 21 + -21 = 0
-21 + -40t + t2 = 0

Begin completing the square.

Move the constant term to the right:

Add '21' to each side of the equation.
-21 + -40t + 21 + t2 = 0 + 21

Reorder the terms:
-21 + 21 + -40t + t2 = 0 + 21

Combine like terms: -21 + 21 = 0
0 + -40t + t2 = 0 + 21
-40t + t2 = 0 + 21

Combine like terms: 0 + 21 = 21
-40t + t2 = 21

The t term is -40t.  Take half its coefficient (-20).
Square it (400) and add it to both sides.

Add '400' to each side of the equation.
-40t + 400 + t2 = 21 + 400

Reorder the terms:
400 + -40t + t2 = 21 + 400

Combine like terms: 21 + 400 = 421
400 + -40t + t2 = 421

Factor a perfect square on the left side:
(t + -20)(t + -20) = 421

Calculate the square root of the right side: 20.518284529

Break this problem into two subproblems by setting 
(t + -20) equal to 20.518284529 and -20.518284529.

Subproblem 1

t + -20 = 20.518284529 Simplifying t + -20 = 20.518284529 Reorder the terms: -20 + t = 20.518284529 Solving -20 + t = 20.518284529 Solving for variable 't'. Move all terms containing t to the left, all other terms to the right. Add '20' to each side of the equation. -20 + 20 + t = 20.518284529 + 20 Combine like terms: -20 + 20 = 0 0 + t = 20.518284529 + 20 t = 20.518284529 + 20 Combine like terms: 20.518284529 + 20 = 40.518284529 t = 40.518284529 Simplifying t = 40.518284529

Subproblem 2

t + -20 = -20.518284529 Simplifying t + -20 = -20.518284529 Reorder the terms: -20 + t = -20.518284529 Solving -20 + t = -20.518284529 Solving for variable 't'. Move all terms containing t to the left, all other terms to the right. Add '20' to each side of the equation. -20 + 20 + t = -20.518284529 + 20 Combine like terms: -20 + 20 = 0 0 + t = -20.518284529 + 20 t = -20.518284529 + 20 Combine like terms: -20.518284529 + 20 = -0.518284529 t = -0.518284529 Simplifying t = -0.518284529

Solution

The solution to the problem is based on the solutions from the subproblems. t = {40.518284529, -0.518284529}

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