If the 100 th term of an arithmetic sequence is 575 , and its common difference is 6 , then its first term $a_{1}=$
its second term $a_{2}=$
its third term $a_{3}=$

Step 1 ：We are given that the 100th term of an arithmetic sequence is 575, and its common difference is 6. We are asked to find the first three terms of the sequence.

Step 2 ：The formula for the nth term of an arithmetic sequence is given by \(a_n = a_1 + (n-1)d\), where \(a_n\) is the nth term, \(a_1\) is the first term, \(n\) is the term number, and \(d\) is the common difference.

Step 3 ：We can rearrange this formula to find the first term: \(a_1 = a_n - (n-1)d\).

Step 4 ：Substituting the given values into the formula, we get \(a_1 = 575 - (100-1)\times 6\).

Step 5 ：Solving the above equation, we find that the first term of the sequence is \(a_{1} = \boxed{-19}\).

Step 6 ：We can find the second term by adding the common difference to the first term: \(a_2 = a_1 + d = -19 + 6\).

Step 7 ：Solving the above equation, we find that the second term of the sequence is \(a_{2} = \boxed{-13}\).

Step 8 ：We can find the third term by adding the common difference to the second term: \(a_3 = a_2 + d = -13 + 6\).

Step 9 ：Solving the above equation, we find that the third term of the sequence is \(a_{3} = \boxed{-7}\).