=(2d+9)(2d-9)

Solution for =(2d+9)(2d-9) equation:

Simplifying
0 = (2d + 9)(2d + -9)

Reorder the terms:
0 = (9 + 2d)(2d + -9)

Reorder the terms:
0 = (9 + 2d)(-9 + 2d)

Multiply (9 + 2d) * (-9 + 2d)
0 = (9(-9 + 2d) + 2d * (-9 + 2d))
0 = ((-9 * 9 + 2d * 9) + 2d * (-9 + 2d))
0 = ((-81 + 18d) + 2d * (-9 + 2d))
0 = (-81 + 18d + (-9 * 2d + 2d * 2d))
0 = (-81 + 18d + (-18d + 4d2))

Combine like terms: 18d + -18d = 0
0 = (-81 + 0 + 4d2)
0 = (-81 + 4d2)

Solving
0 = -81 + 4d2

Solving for variable 'd'.

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

Add '-4d2' to each side of the equation.
0 + -4d2 = -81 + 4d2 + -4d2
Remove the zero:
-4d2 = -81 + 4d2 + -4d2

Combine like terms: 4d2 + -4d2 = 0
-4d2 = -81 + 0
-4d2 = -81

Divide each side by '-4'.
d2 = 20.25

Simplifying
d2 = 20.25

Take the square root of each side:
d = {-4.5, 4.5}