Which is the fully factored form of 49x^30-21x^15+7x^5?

7x5(7x25-3x10+1)

7x5(7x6-3x3+x)

7x5(7x25-3x10)

7x5(7x6-3x3)

The fully factored form of 49x^30 - 21x^15 + 7x^5 is 7x^5(7x^25 - 3x^10 + 1)