中一英文數學

6, -3, -12, -21...
The next two terms are - 30, - 39

Determine what kind of sequence it is?
It is _arithmetic___ sequence.
Comment:2nd term – 1st term = (-3) – (6) = -93rd term – 2nd term = (-12) – (-3) = -94th term – 3rd term = (-21) – (-12) = -9 So the common difference is =-9The first term is 6
The general term of an arithmetic sequence is given by:tn = a + (n – 1) d where a is the first term, n the number of term, and d is the common difference.In the above example, a = 6 and d = -91st term = 62nd term, t2 = 6+(2 -1)(-9) = -33rd term, t3 = 6+(3 -1)(-9) = -124th term, t4 = 6+(4 -1)(-9) = -215th term, t5 = 6+(5 -1)(-9) = -30; It can also be obtained by (-21) + (-9) = -306th term, t6 = 6+(6 -1)(-9) = -39; It can also be obtained by (-30) + (-9) = -30

6,-3,-12,-21...
6 -9 =-3 -9 =-12 -9 =-21 -9 =-30 -9=-39
The next two terms are -30 , -39 .


Dertermine(determine ?) what kind of sequence it is?
It is big to small (i am not sure) sequence.