Question

factor the polynomial 21cd - 3d

Answer 1

Hmmm are you familiar with factoring?

Answer 2

So basically we are pulling out a variable or value that both terms have

Answer 3

So for example:
ab+bc
Both terms have b so we pull out the b
b(a+b)

Answer 4

21cd - 3d
What value or variable do both terms have?