(9-d)*9*(9+d)=693

Solution for (9-d)*9*(9+d)=693 equation:

Simplifying
(9 + -1d) * 9(9 + d) = 693

Reorder the terms for easier multiplication:
9(9 + -1d)(9 + d) = 693

Multiply (9 + -1d) * (9 + d)
9(9(9 + d) + -1d * (9 + d)) = 693
9((9 * 9 + d * 9) + -1d * (9 + d)) = 693
9((81 + 9d) + -1d * (9 + d)) = 693
9(81 + 9d + (9 * -1d + d * -1d)) = 693
9(81 + 9d + (-9d + -1d2)) = 693

Combine like terms: 9d + -9d = 0
9(81 + 0 + -1d2) = 693
9(81 + -1d2) = 693
(81 * 9 + -1d2 * 9) = 693
(729 + -9d2) = 693

Solving
729 + -9d2 = 693

Solving for variable 'd'.

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

Add '-729' to each side of the equation.
729 + -729 + -9d2 = 693 + -729

Combine like terms: 729 + -729 = 0
0 + -9d2 = 693 + -729
-9d2 = 693 + -729

Combine like terms: 693 + -729 = -36
-9d2 = -36

Divide each side by '-9'.
d2 = 4

Simplifying
d2 = 4

Take the square root of each side:
d = {-2, 2}