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Maths Exercices
Write variable expressions for arithmetic sequences

Write an expression to describe the sequence -3, -6, -9, -12,... Use n to represent the position of a term in the sequence, where n=1 for the first term.

The sequence -3, -6, -9, -12,... looks like 1, 2, 3, 4,... except each term is multiplied by -3. So, the formula is -3n, where n represents the position of a term in the sequence.

Check the first four terms:

To find the 1st term, plug in n=1.
-3n=-3(1)=-3

To find the 2nd term, plug in n=2.
-3n=-3(2)=-6

To find the 3rd term, plug in n=3.
-3n=-3(3)=-9

To find the 4th term, plug in n=4.
-3n=-3(4)=-12

The sequence -3, -6, -9, -12,... is described by the expression -3n


Write an expression to describe the sequence -7, -6, -5, -4,... Use n to represent the position of a term in the sequence, where n=1 for the first term.

The sequence -7, -6, -5, -4,... looks like 1, 2, 3, 4,... except each term is 8 smaller. So, the formula is n-8, where n represents the position of a term in the sequence.

Check the first four terms:

To find the 1st term, plug in n=1.
n-8=1-8=-7

To find the 2nd term, plug in n=2.
n-8=2-8=-6

To find the 3rd term, plug in n=3.
n-8=3-8=-5

To find the 4th term, plug in n=4.
n-8=4-8=-4

The sequence -7, -6, -5, -4,... is described by the expression n-8.