3r^2+5r+12=0

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Solution for 3r^2+5r+12=0 equation:


Simplifying
3r2 + 5r + 12 = 0

Reorder the terms:
12 + 5r + 3r2 = 0

Solving
12 + 5r + 3r2 = 0

Solving for variable 'r'.

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

Divide each side by '3'.
4 + 1.666666667r + r2 = 0

Move the constant term to the right:

Add '-4' to each side of the equation.
4 + 1.666666667r + -4 + r2 = 0 + -4

Reorder the terms:
4 + -4 + 1.666666667r + r2 = 0 + -4

Combine like terms: 4 + -4 = 0
0 + 1.666666667r + r2 = 0 + -4
1.666666667r + r2 = 0 + -4

Combine like terms: 0 + -4 = -4
1.666666667r + r2 = -4

The r term is 1.666666667r.  Take half its coefficient (0.8333333335).
Square it (0.6944444447) and add it to both sides.

Add '0.6944444447' to each side of the equation.
1.666666667r + 0.6944444447 + r2 = -4 + 0.6944444447

Reorder the terms:
0.6944444447 + 1.666666667r + r2 = -4 + 0.6944444447

Combine like terms: -4 + 0.6944444447 = -3.3055555553
0.6944444447 + 1.666666667r + r2 = -3.3055555553

Factor a perfect square on the left side:
(r + 0.8333333335)(r + 0.8333333335) = -3.3055555553

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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