Answer:
[tex]\boxed{7x^2y^4z}[/tex]
Step-by-step explanation:
The greatest common factor of 21=7·3 and 28=7·4 is 7.
The greatest common factor of x^4 and x^2 is x^2 (the term with the smallest exponent).
The greatest common factor of y^5 and y^4 is y^4.
The greatest common factor of z and z^4 is z.
21x^4·y^5·z+28x^2·y^4·z^4 = 7x^2·y^4·z·(3x^2·y + 4z^3)
