(7c+3D)(7c-3D)=

Solution for (7c+3D)(7c-3D)= equation:

Simplifying
(7c + 3D)(7c + -3D) = 0

Reorder the terms:
(3D + 7c)(7c + -3D) = 0

Reorder the terms:
(3D + 7c)(-3D + 7c) = 0

Multiply (3D + 7c) * (-3D + 7c)
(3D * (-3D + 7c) + 7c * (-3D + 7c)) = 0
((-3D * 3D + 7c * 3D) + 7c * (-3D + 7c)) = 0
((-9D2 + 21cD) + 7c * (-3D + 7c)) = 0
(-9D2 + 21cD + (-3D * 7c + 7c * 7c)) = 0
(-9D2 + 21cD + (-21cD + 49c2)) = 0

Combine like terms: 21cD + -21cD = 0
(-9D2 + 0 + 49c2) = 0
(-9D2 + 49c2) = 0

Solving
-9D2 + 49c2 = 0

Solving for variable 'D'.

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

Add '-49c2' to each side of the equation.
-9D2 + 49c2 + -49c2 = 0 + -49c2

Combine like terms: 49c2 + -49c2 = 0
-9D2 + 0 = 0 + -49c2
-9D2 = 0 + -49c2
Remove the zero:
-9D2 = -49c2

Divide each side by '-9'.
D2 = 5.444444444c2

Simplifying
D2 = 5.444444444c2

Take the square root of each side:
D = {-2.333333333c, 2.333333333c}