Question

the end term of an ap is given by minus 4n + 15 find the sum of first 20 terms of this AP​

Answer 1

Answer:

4n+15

Put n=1,2,3,4ete

we get the Ap,19,23,2731 .....

1st term=19,d=4, n=20

S20=20/2{19x2+(20-1) 4}

lo{38 +19x4}

10x11= 1140. Ans