-21r^2+13r-10=0

Solution for -21r^2+13r-10=0 equation:

Simplifying
-21r2 + 13r + -10 = 0

Reorder the terms:
-10 + 13r + -21r2 = 0

Solving
-10 + 13r + -21r2 = 0

Solving for variable 'r'.

Begin completing the square.  Divide all terms by
-21 the coefficient of the squared term: 

Divide each side by '-21'.
0.4761904762 + -0.619047619r + r2 = 0

Move the constant term to the right:

Add '-0.4761904762' to each side of the equation.
0.4761904762 + -0.619047619r + -0.4761904762 + r2 = 0 + -0.4761904762

Reorder the terms:
0.4761904762 + -0.4761904762 + -0.619047619r + r2 = 0 + -0.4761904762

Combine like terms: 0.4761904762 + -0.4761904762 = 0.0000000000
0.0000000000 + -0.619047619r + r2 = 0 + -0.4761904762
-0.619047619r + r2 = 0 + -0.4761904762

Combine like terms: 0 + -0.4761904762 = -0.4761904762
-0.619047619r + r2 = -0.4761904762

The r term is -0.619047619r.  Take half its coefficient (-0.3095238095).
Square it (0.09580498865) and add it to both sides.

Add '0.09580498865' to each side of the equation.
-0.619047619r + 0.09580498865 + r2 = -0.4761904762 + 0.09580498865

Reorder the terms:
0.09580498865 + -0.619047619r + r2 = -0.4761904762 + 0.09580498865

Combine like terms: -0.4761904762 + 0.09580498865 = -0.38038548755
0.09580498865 + -0.619047619r + r2 = -0.38038548755

Factor a perfect square on the left side:
(r + -0.3095238095)(r + -0.3095238095) = -0.38038548755

Can't calculate square root of the right side.

The solution to this equation could not be determined.