Question

here,a=t1=6,d=6,tn=78,n=?,Sn=?​

Answer 1

Answer:

• n=(84-t1)/6
• n=(84-t1)/6Sn=-t1^2+6t1+6552

Step-by-step explanation:

1. tn=a+(n-1)d
2. tn=a+(n-1)d78=t1+(n-1)6
3. tn=a+(n-1)d78=t1+(n-1)6n=(78-t1)/6 +1
4. tn=a+(n-1)d78=t1+(n-1)6n=(78-t1)/6 +1n=(84-t1)/6

• tn=a+(n-1)d78=t1+(n-1)6n=(78-t1)/6 +1n=(84-t1)/6Sn=n/2(a+tn)
• tn=a+(n-1)d78=t1+(n-1)6n=(78-t1)/6 +1n=(84-t1)/6Sn=n/2(a+tn)Sn=(84-t1)/12(t1+78)
• tn=a+(n-1)d78=t1+(n-1)6n=(78-t1)/6 +1n=(84-t1)/6Sn=n/2(a+tn)Sn=(84-t1)/12(t1+78)Sn=-t1^2+6t1+6552