(9c-7d)(9c+7d)=0

Solution for (9c-7d)(9c+7d)=0 equation:

Simplifying
(9c + -7d)(9c + 7d) = 0

Multiply (9c + -7d) * (9c + 7d)
(9c * (9c + 7d) + -7d * (9c + 7d)) = 0
((9c * 9c + 7d * 9c) + -7d * (9c + 7d)) = 0

Reorder the terms:
((63cd + 81c2) + -7d * (9c + 7d)) = 0
((63cd + 81c2) + -7d * (9c + 7d)) = 0
(63cd + 81c2 + (9c * -7d + 7d * -7d)) = 0
(63cd + 81c2 + (-63cd + -49d2)) = 0

Reorder the terms:
(63cd + -63cd + 81c2 + -49d2) = 0

Combine like terms: 63cd + -63cd = 0
(0 + 81c2 + -49d2) = 0
(81c2 + -49d2) = 0

Solving
81c2 + -49d2 = 0

Solving for variable 'c'.

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

Add '49d2' to each side of the equation.
81c2 + -49d2 + 49d2 = 0 + 49d2

Combine like terms: -49d2 + 49d2 = 0
81c2 + 0 = 0 + 49d2
81c2 = 0 + 49d2
Remove the zero:
81c2 = 49d2

Divide each side by '81'.
c2 = 0.6049382716d2

Simplifying
c2 = 0.6049382716d2

Take the square root of each side:
c = {-0.777777778d, 0.777777778d}