A^4 - 16 = (A^2 + 4)(A^2 - 4) = (A^2 + 4)(A + 2)(A - 2)
49 - b^4 = (7 + b^2)(7 - b^2) = (7 + b^2)(7 + b)(7 - b)
A^4 - 16 = (A^2 + 4)(A^2 - 4) = (A^2 + 4)(A + 2)(A - 2)
49 - b^4 = (7 + b^2)(7 - b^2) = (7 + b^2)(7 + b)(7 - b)