Find the sum of the first 90 terms of the sequence –4, –1, 2, 5, 8, ...

asked Mar 15, 2018 82.5k views

3 votes

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2 votes

Answer:

11655 is correct

Explanation:

Chlorie answered Mar 17, 2018

6.6k points

5 votes

Hello :
-1-(-4) =2-(-1)=5-2=8-5=3 ( arhtmitic sequence r= 3)
Un = U1+(n-1)r
U90 = -4+(90-1)(3)= 263
sum = n/2 (U1 +U90)
sum = 90/2(-4+263) = 11655

Jabda answered Mar 19, 2018

by Jabda

5.5k points

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