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The sum of the first 20 terms of an arithmetic sequence with a common difference of 3 is 650. find the first term

Respuesta :

VivaciousLyla
Hey You!

Okay, so your Problem will:

650 = 20/2{2a + (20-1)3}
Or 650 = 10{2a + 57}
Or 650 - 570=20a
Or 80/20=a

So, the first term would be 4.
[tex]<b><i>HLLO there!![/tex]

As we know that ..

Sn = n/2{2a + (n-1)d} ........1️⃣

So accordingly here
▪️Sn( sum of terms )= 650
▪️n( terms ) = 20
▪️d ( difference ) = 3

So we have to find now a( first term )

put all the above values in formula 1️⃣

650 = 20/2{ 2a+( 20-1)3}
=>650 = 10 { 2a+ 57 }
=> 20a = 650 - 570
=> a = 80/20
=> a = 4

So the first term is 4 .


HOPE IT HELPED YOU.