Question

7. a) Write the arithmetic sequence with first term 1 and common difference 42?
b) Find its 31st term?
c) Calculate the sum of its first 31 terms?​

Answer 1

a31=1+(31-1)42

=1+(30)42

=1+1260

=1261

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Answer 2

a1=1 (given)

d=42 (given)

a) a2=a1+d=1+42=43

=>a3=a2+d=43+42=85

and so.....on

1,43,85,..........

b)TO FIND A PARTICULAR TERM WE HAVE A FORMULA

=>An=a+(n-1)d

An=nth term

a=first term

d=common difference

An=?

a=first term

n=31 (given)

d=common difference

NOW APPLY THE FORMULA:

A31=1+(31-1)42

A31=1+1260

A31=1261

c)TO CALCULATE SUM THE FORMULA IS

=>Sn=n/2 (2a+(n-1)d)

Sn=sum upto n terms

n,a,d are already said above

S31=31/2 (2×1 + (31-1)42)

S31=31/2 × 2520

S31=31×1260

S31=39060