the formula is a_{1}+(n-1) d
so a_{1} would be the first number in the sequence, which would be 13 in problem 9.
13+(n-1)d
then you put in n, which is 10 (it represents which number in the sequence you're looking for, for example 16 is the second number in the sequence)
13+(10-1)d
then you find the difference between each number, represented by d which in this case is 3
13+(10-1)3
13+(9)3
13+27=
40
Answer:
an = 5n -7
Step-by-step explanation:
Try the offered formulas with n= 1 and see which gives you the first term of the sequence.
<u>an = -2n +3</u>
-2(1) +3 = 1 . . . . not -2
<u>an = -2n +7</u>
-2(1) +7 = 5 . . . . not -2
<u>an = 5n +3</u>
5(1) +3 = 8 . . . . not -2
<u>an = 5n -7</u>
5(1) -7 = -2 . . . . this is the formula you want
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If you recognize the common difference of the sequence to be 5, then you can automatically eliminate any formulas that don't contain 5n.
The only example that does not have parallel congruent bases is the rectangular pyramid. The reason is that all pyramids are formed from a base and then all lateral faces are triangles meeting at one point on the top of the pyramid.
