<image> Read the following passage and solve the problems below. Observe the following sequence: 1, 2, 4, 8, …, we find that from the second term onwards, each term is equal to the previous term multiplied by 2. Generally, if a sequence has the property that from the second term onwards, each term is equal to the previous term multiplied by the same constant, it is called a geometric sequence, and this constant is called the common ratio of the geometric sequence.
(1) The fourth term of the geometric sequence 5, -15, 45, … is ________.
(2) If a sequence a_{1}, a_{2}, a_{3}, a_{4}, … is a geometric sequence and the common ratio is q, then according to the above definition, we have a_{2}=a_{1}q, a_{3}=a_{2}q=(a_{1}q)q=a_{1}q^{2}, a_{4}=a_{3}q=(a_{1}q^{2})q=a_{1}q^{3}, …, so an=_________ (expressed as an algebraic expression containing a_{1} and q).
(3) The second term of a geometric sequence is 10, and the third term is 20. Then its first term is ________, and the fourth term is ________.