5t^2+13t-21=0

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Solution for 5t^2+13t-21=0 equation:


Simplifying
5t2 + 13t + -21 = 0

Reorder the terms:
-21 + 13t + 5t2 = 0

Solving
-21 + 13t + 5t2 = 0

Solving for variable 't'.

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

Divide each side by '5'.
-4.2 + 2.6t + t2 = 0

Move the constant term to the right:

Add '4.2' to each side of the equation.
-4.2 + 2.6t + 4.2 + t2 = 0 + 4.2

Reorder the terms:
-4.2 + 4.2 + 2.6t + t2 = 0 + 4.2

Combine like terms: -4.2 + 4.2 = 0.0
0.0 + 2.6t + t2 = 0 + 4.2
2.6t + t2 = 0 + 4.2

Combine like terms: 0 + 4.2 = 4.2
2.6t + t2 = 4.2

The t term is 2.6t.  Take half its coefficient (1.3).
Square it (1.69) and add it to both sides.

Add '1.69' to each side of the equation.
2.6t + 1.69 + t2 = 4.2 + 1.69

Reorder the terms:
1.69 + 2.6t + t2 = 4.2 + 1.69

Combine like terms: 4.2 + 1.69 = 5.89
1.69 + 2.6t + t2 = 5.89

Factor a perfect square on the left side:
(t + 1.3)(t + 1.3) = 5.89

Calculate the square root of the right side: 2.42693222

Break this problem into two subproblems by setting 
(t + 1.3) equal to 2.42693222 and -2.42693222.

Subproblem 1

t + 1.3 = 2.42693222 Simplifying t + 1.3 = 2.42693222 Reorder the terms: 1.3 + t = 2.42693222 Solving 1.3 + t = 2.42693222 Solving for variable 't'. Move all terms containing t to the left, all other terms to the right. Add '-1.3' to each side of the equation. 1.3 + -1.3 + t = 2.42693222 + -1.3 Combine like terms: 1.3 + -1.3 = 0.0 0.0 + t = 2.42693222 + -1.3 t = 2.42693222 + -1.3 Combine like terms: 2.42693222 + -1.3 = 1.12693222 t = 1.12693222 Simplifying t = 1.12693222

Subproblem 2

t + 1.3 = -2.42693222 Simplifying t + 1.3 = -2.42693222 Reorder the terms: 1.3 + t = -2.42693222 Solving 1.3 + t = -2.42693222 Solving for variable 't'. Move all terms containing t to the left, all other terms to the right. Add '-1.3' to each side of the equation. 1.3 + -1.3 + t = -2.42693222 + -1.3 Combine like terms: 1.3 + -1.3 = 0.0 0.0 + t = -2.42693222 + -1.3 t = -2.42693222 + -1.3 Combine like terms: -2.42693222 + -1.3 = -3.72693222 t = -3.72693222 Simplifying t = -3.72693222

Solution

The solution to the problem is based on the solutions from the subproblems. t = {1.12693222, -3.72693222}

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