greetings! could you help me with the following questions?

1.In the expansion of (ax + by)⁶, the first three terms are 729x⁶, 7290x⁵y, and 30375x⁴y². Find the values of a and b.

1.Show algebraically that for any n and r where , the following must always be true:(n/ n-r)= (n/r)

1.Find the prime factors of 209053845. What is the total number of divisors of 209053845 including 1 and itself?

thankyou!!!