katiebugg Group Title The third term of an arithmetic sequence is 9 and the seventh term is 31. Find the sum of the first twenty-two terms. one year ago one year ago

1. helder_edwin Group Title

an arithmetic sequence is of the form $\large a_1\qquad\text{not given}$ $\large a_2=a_1+d$ $\large 9=a_3=a_2+d=a_1+2d$ so $\large 31=a_7=a_1+6d$

2. helder_edwin Group Title

u end up with $\large 9=a_1+2d$ $\large 31=a_1+6d$ solve this system

3. helder_edwin Group Title

r u there @katiebugg ?

4. katiebugg Group Title

sorry yeahh was working on a prob thanks!!!