1 + 3 + 5 + 7 +..........x = 12544 ; x is the last term of the sequence. What will be the value of x ?

Question

In the sequence of numbers 4,7,-7,....., the first term is 4. Each even numbered term is 3 more than the previous term.Each odd numbered term after the first is -1 times the previous term. What is the sum of the first 22 terms?

Answer 1

12544=n/2 *(2*1+(n-1)*2)
n=112
So
Last term=a+(n-1)*d=1+(112-1)*2
=223