1) ax^2 - ay = a(x^2 - y).
2) 7a^2 - 14ab + 7b^2 = 7(a^2 - 2ab + b^2) = 7(a - b)^2.
3)y - 100y^3 = y(1 - 100y^2) = y(1 + 10y)(1 - 10Y).
4) 16 - y^4 = 4^2 - (y^2)^2 = (4 + y^2)(4 - y^2) = (4 + y^2)(2 + y)(2 - y).
1) ax^2 - ay = a(x^2 - y).
2) 7a^2 - 14ab + 7b^2 = 7(a^2 - 2ab + b^2) = 7(a - b)^2.
3)y - 100y^3 = y(1 - 100y^2) = y(1 + 10y)(1 - 10Y).
4) 16 - y^4 = 4^2 - (y^2)^2 = (4 + y^2)(4 - y^2) = (4 + y^2)(2 + y)(2 - y).