-4.9x^2+21x=55

Solution for -4.9x^2+21x=55 equation:

Simplifying
-4.9x2 + 21x = 55

Reorder the terms:
21x + -4.9x2 = 55

Solving
21x + -4.9x2 = 55

Solving for variable 'x'.

Reorder the terms:
-55 + 21x + -4.9x2 = 55 + -55

Combine like terms: 55 + -55 = 0
-55 + 21x + -4.9x2 = 0

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

Divide each side by '-4.9'.
11.2244898 + -4.285714286x + x2 = 0

Move the constant term to the right:

Add '-11.2244898' to each side of the equation.
11.2244898 + -4.285714286x + -11.2244898 + x2 = 0 + -11.2244898

Reorder the terms:
11.2244898 + -11.2244898 + -4.285714286x + x2 = 0 + -11.2244898

Combine like terms: 11.2244898 + -11.2244898 = 0.0000000
0.0000000 + -4.285714286x + x2 = 0 + -11.2244898
-4.285714286x + x2 = 0 + -11.2244898

Combine like terms: 0 + -11.2244898 = -11.2244898
-4.285714286x + x2 = -11.2244898

The x term is -4.285714286x.  Take half its coefficient (-2.142857143).
Square it (4.591836735) and add it to both sides.

Add '4.591836735' to each side of the equation.
-4.285714286x + 4.591836735 + x2 = -11.2244898 + 4.591836735

Reorder the terms:
4.591836735 + -4.285714286x + x2 = -11.2244898 + 4.591836735

Combine like terms: -11.2244898 + 4.591836735 = -6.632653065
4.591836735 + -4.285714286x + x2 = -6.632653065

Factor a perfect square on the left side:
(x + -2.142857143)(x + -2.142857143) = -6.632653065

Can't calculate square root of the right side.

The solution to this equation could not be determined.