5(3d+6d-4d^2+6)-6=448

Solution for 5(3d+6d-4d^2+6)-6=448 equation:

Simplifying
5(3d + 6d + -4d2 + 6) + -6 = 448

Reorder the terms:
5(6 + 3d + 6d + -4d2) + -6 = 448

Combine like terms: 3d + 6d = 9d
5(6 + 9d + -4d2) + -6 = 448
(6 * 5 + 9d * 5 + -4d2 * 5) + -6 = 448
(30 + 45d + -20d2) + -6 = 448

Reorder the terms:
30 + -6 + 45d + -20d2 = 448

Combine like terms: 30 + -6 = 24
24 + 45d + -20d2 = 448

Solving
24 + 45d + -20d2 = 448

Solving for variable 'd'.

Reorder the terms:
24 + -448 + 45d + -20d2 = 448 + -448

Combine like terms: 24 + -448 = -424
-424 + 45d + -20d2 = 448 + -448

Combine like terms: 448 + -448 = 0
-424 + 45d + -20d2 = 0

Begin completing the square.  Divide all terms by
-20 the coefficient of the squared term: 

Divide each side by '-20'.
21.2 + -2.25d + d2 = 0.0

Move the constant term to the right:

Add '-21.2' to each side of the equation.
21.2 + -2.25d + -21.2 + d2 = 0.0 + -21.2

Reorder the terms:
21.2 + -21.2 + -2.25d + d2 = 0.0 + -21.2

Combine like terms: 21.2 + -21.2 = 0.0
0.0 + -2.25d + d2 = 0.0 + -21.2
-2.25d + d2 = 0.0 + -21.2

Combine like terms: 0.0 + -21.2 = -21.2
-2.25d + d2 = -21.2

The d term is -2.25d.  Take half its coefficient (-1.125).
Square it (1.265625) and add it to both sides.

Add '1.265625' to each side of the equation.
-2.25d + 1.265625 + d2 = -21.2 + 1.265625

Reorder the terms:
1.265625 + -2.25d + d2 = -21.2 + 1.265625

Combine like terms: -21.2 + 1.265625 = -19.934375
1.265625 + -2.25d + d2 = -19.934375

Factor a perfect square on the left side:
(d + -1.125)(d + -1.125) = -19.934375

Can't calculate square root of the right side.

The solution to this equation could not be determined.