Sum of first n terms of an arithmetic sequence is 5n² + 2n. What is the 21st term of the sequence ?A102B107C202D207Answer: D. 207 Read Explanation: Pn2+qnPn^2+qnPn2+qnp=d2p=\frac{d}{2}p=2dp+q=fp+q=fp+q=fd=5×2=10d=5\times 2 = 10d=5×2=105+2=f5+2=f5+2=fx21=f+20d=7+20×10=207x_{21}=f+20d=7+20\times10=207x21=f+20d=7+20×10=207 Read more in App