What polynomial identity should be used to prove that 21=25-4?
A: Difference of cubes
B: Difference of Squares
C: Square of Binomial
D: Sum of Cubes

Question

What polynomial identity should be used to prove that 21=25-4?
A: Difference of cubes 
B: Difference of Squares 
C: Square of Binomial
D: Sum of Cubes

anonymous · Answer

hi

anonymous · Answer

b) i think but im not sure  let joanne answer

joannablackwelder · Answer

Hmm, 25-4 looks like difference of squares, but not sure how that helps you prove it.

anonymous · Answer

I thought  it was c but im not positive.

zpupster · Answer

i had to look this one up.

a 2 - b 2 = (a+b)(a-b) (Difference of squares)

5^2 - 2^2

lets see

(5+2)(5-2) = ?

joannablackwelder · Answer

Yeah, @zpupster , that works. I'm just not sure how it proves the statement.