-4.9t^2+20t+1.8=0

Solution for -4.9t^2+20t+1.8=0 equation:

Simplifying
-4.9t2 + 20t + 1.8 = 0

Reorder the terms:
1.8 + 20t + -4.9t2 = 0

Solving
1.8 + 20t + -4.9t2 = 0

Solving for variable 't'.

Begin completing the square.  Divide all terms by
-4.9 the coefficient of the squared term: 

Divide each side by '-4.9'.
-0.3673469388 + -4.081632653t + t2 = 0

Move the constant term to the right:

Add '0.3673469388' to each side of the equation.
-0.3673469388 + -4.081632653t + 0.3673469388 + t2 = 0 + 0.3673469388

Reorder the terms:
-0.3673469388 + 0.3673469388 + -4.081632653t + t2 = 0 + 0.3673469388

Combine like terms: -0.3673469388 + 0.3673469388 = 0.0000000000
0.0000000000 + -4.081632653t + t2 = 0 + 0.3673469388
-4.081632653t + t2 = 0 + 0.3673469388

Combine like terms: 0 + 0.3673469388 = 0.3673469388
-4.081632653t + t2 = 0.3673469388

The t term is -4.081632653t.  Take half its coefficient (-2.040816327).
Square it (4.164931281) and add it to both sides.

Add '4.164931281' to each side of the equation.
-4.081632653t + 4.164931281 + t2 = 0.3673469388 + 4.164931281

Reorder the terms:
4.164931281 + -4.081632653t + t2 = 0.3673469388 + 4.164931281

Combine like terms: 0.3673469388 + 4.164931281 = 4.5322782198
4.164931281 + -4.081632653t + t2 = 4.5322782198

Factor a perfect square on the left side:
(t + -2.040816327)(t + -2.040816327) = 4.5322782198

Calculate the square root of the right side: 2.128914799

Break this problem into two subproblems by setting 
(t + -2.040816327) equal to 2.128914799 and -2.128914799.

Subproblem 1
t + -2.040816327 = 2.128914799

Simplifying
t + -2.040816327 = 2.128914799

Reorder the terms:
-2.040816327 + t = 2.128914799

Solving
-2.040816327 + t = 2.128914799

Solving for variable 't'.

Move all terms containing t to the left, all other terms to the right.

Add '2.040816327' to each side of the equation.
-2.040816327 + 2.040816327 + t = 2.128914799 + 2.040816327

Combine like terms: -2.040816327 + 2.040816327 = 0.000000000
0.000000000 + t = 2.128914799 + 2.040816327
t = 2.128914799 + 2.040816327

Combine like terms: 2.128914799 + 2.040816327 = 4.169731126
t = 4.169731126

Simplifying
t = 4.169731126

Subproblem 2
t + -2.040816327 = -2.128914799

Simplifying
t + -2.040816327 = -2.128914799

Reorder the terms:
-2.040816327 + t = -2.128914799

Solving
-2.040816327 + t = -2.128914799

Solving for variable 't'.

Move all terms containing t to the left, all other terms to the right.

Add '2.040816327' to each side of the equation.
-2.040816327 + 2.040816327 + t = -2.128914799 + 2.040816327

Combine like terms: -2.040816327 + 2.040816327 = 0.000000000
0.000000000 + t = -2.128914799 + 2.040816327
t = -2.128914799 + 2.040816327

Combine like terms: -2.128914799 + 2.040816327 = -0.088098472
t = -0.088098472

Simplifying
t = -0.088098472

Solution
The solution to the problem is based on the solutions
from the subproblems.
t = {4.169731126, -0.088098472}