28d^2-78=-15

Solution for 28d^2-78=-15 equation:

Simplifying
28d2 + -78 = -15

Reorder the terms:
-78 + 28d2 = -15

Solving
-78 + 28d2 = -15

Solving for variable 'd'.

Move all terms containing d to the left, all other terms to the right.

Add '78' to each side of the equation.
-78 + 78 + 28d2 = -15 + 78

Combine like terms: -78 + 78 = 0
0 + 28d2 = -15 + 78
28d2 = -15 + 78

Combine like terms: -15 + 78 = 63
28d2 = 63

Divide each side by '28'.
d2 = 2.25

Simplifying
d2 = 2.25

Take the square root of each side:
d = {-1.5, 1.5}