-4t^2+18t+81=0

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Solution for -4t^2+18t+81=0 equation:


Simplifying
-4t2 + 18t + 81 = 0

Reorder the terms:
81 + 18t + -4t2 = 0

Solving
81 + 18t + -4t2 = 0

Solving for variable 't'.

Begin completing the square.  Divide all terms by
-4 the coefficient of the squared term: 

Divide each side by '-4'.
-20.25 + -4.5t + t2 = 0

Move the constant term to the right:

Add '20.25' to each side of the equation.
-20.25 + -4.5t + 20.25 + t2 = 0 + 20.25

Reorder the terms:
-20.25 + 20.25 + -4.5t + t2 = 0 + 20.25

Combine like terms: -20.25 + 20.25 = 0.00
0.00 + -4.5t + t2 = 0 + 20.25
-4.5t + t2 = 0 + 20.25

Combine like terms: 0 + 20.25 = 20.25
-4.5t + t2 = 20.25

The t term is -4.5t.  Take half its coefficient (-2.25).
Square it (5.0625) and add it to both sides.

Add '5.0625' to each side of the equation.
-4.5t + 5.0625 + t2 = 20.25 + 5.0625

Reorder the terms:
5.0625 + -4.5t + t2 = 20.25 + 5.0625

Combine like terms: 20.25 + 5.0625 = 25.3125
5.0625 + -4.5t + t2 = 25.3125

Factor a perfect square on the left side:
(t + -2.25)(t + -2.25) = 25.3125

Calculate the square root of the right side: 5.031152949

Break this problem into two subproblems by setting 
(t + -2.25) equal to 5.031152949 and -5.031152949.

Subproblem 1

t + -2.25 = 5.031152949 Simplifying t + -2.25 = 5.031152949 Reorder the terms: -2.25 + t = 5.031152949 Solving -2.25 + t = 5.031152949 Solving for variable 't'. Move all terms containing t to the left, all other terms to the right. Add '2.25' to each side of the equation. -2.25 + 2.25 + t = 5.031152949 + 2.25 Combine like terms: -2.25 + 2.25 = 0.00 0.00 + t = 5.031152949 + 2.25 t = 5.031152949 + 2.25 Combine like terms: 5.031152949 + 2.25 = 7.281152949 t = 7.281152949 Simplifying t = 7.281152949

Subproblem 2

t + -2.25 = -5.031152949 Simplifying t + -2.25 = -5.031152949 Reorder the terms: -2.25 + t = -5.031152949 Solving -2.25 + t = -5.031152949 Solving for variable 't'. Move all terms containing t to the left, all other terms to the right. Add '2.25' to each side of the equation. -2.25 + 2.25 + t = -5.031152949 + 2.25 Combine like terms: -2.25 + 2.25 = 0.00 0.00 + t = -5.031152949 + 2.25 t = -5.031152949 + 2.25 Combine like terms: -5.031152949 + 2.25 = -2.781152949 t = -2.781152949 Simplifying t = -2.781152949

Solution

The solution to the problem is based on the solutions from the subproblems. t = {7.281152949, -2.781152949}

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