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# arithmetic series probelm Watch

1. The third term of an arithmetic series is 5 and the fifth term is 9.Find the first term and the common difference.
2. is there no other information?
3. Use the formula un = a + (n-1)d
Form two simultaneous equations and solve for the values you want.

Or you can do it by inspection.
4. Posted from TSR Mobile
Ty and how by inspection.
5. first term is one as theres a difference of four between 5 and 9 divide four by two = 2

the a+ (n-1)d = 5

5 = a + (2)2

5-4=1

i think it should tell you the sum of the series to work out the last on but i may be wrong.
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Ty!!! Exactly want the answer says.Cheers future Gauss; ) .
Posted from TSR Mobile
Ty and how by inspection.
By inspection:
d = (9-5)/2
d = 2
Then 5 = a + (3-1)2
5 = a + 4
a = 1

Or by formula:
9 = a + (5-1)d
9 = a + 4d [1]

then
5 = a + (3-1)d
5 = a + 2d [2]

[1] - [2]: 4 = 2d
d = 2 [3]

sub [3] into [2]: 5 = a + 4
a = 1
8. Posted from TSR Mobile

Ty may you be given a fields medal one day: ) .

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