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The sum of the first 21 terms of the progression, -18, -15, -12,...is?

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For any AP,
Sn = n/2 (2a + (n-1) d)
So plug in your numbers.

-630

find the sum of the 21 term of the progression -18-15-12 ?

252 is the answer

The sum of the first 21 term of the progrestion- 18-15,-12--- is

I got 252 too I don't know if I am correct

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