Question 257426
3x+4-(2x+4)=x subtract the 1st term from the 3rd term
The difference between the 2nd and 1st term must be half of x or .5x
2x+4+ .5x =5x-4
2.5x=8
x=3.2
d=.5*3.2=1.6 difference between each number.
Now we can find the 10th term.
{{{a[n]=dn+(a[1]-d)}}}
{{{a[10]=(1.6*10)+10.4-1.6}}}
=24.8
{{{S[n]=(n/2)(a[1]+a[n])}}} formula for the sum of a finite arithmetic sequence.
{{{S[10]=(10/2)(10.4+24.8)}}}
=176
.
Ed