11111111111111111111111111111111111 11111111111111111111111111111111111 111111111

Which one ? is the answer and how to find this answer

45 was divided by a power of ten to get 4.5. what power of ten was it divided by? people 4.5

Simplify (4x^2 - 8xy + 2y^2) - (9x^2 - 4xy - 7y^2) a. -5x^2 + 4xy + 9y^2 b. -5x^2 - 4xy + 9y^2 c. -5x^2 + 12xy + 4y^2 d. -5x^2 - 4xy - 5y^2