How do you factor completely `21cd-3d`?

Related questions

• What is Factoring Completely?
• How do you know when you have completely factored a polynomial?
• Which methods of factoring do you use to factor completely?
• How do you factor completely `2x^2-8`?
• Which method do you use to factor `3x(x-1)+4(x-1)`?
• What are the factors of `12x^3+12x^2+3x`?
• How do you find the two numbers by using the factoring method, if one number is seven more than...
• How do you factor `12c^2-75` completely?
• How do you factor `x^6-26x^3-27`?
• How do you factor `100x^2+180x+81`?