Two APs have the same common difference. The first term of one of these is -1 and that of the other

Question

Two APs have the same common difference. The first term of one of these is -1 and that of the other is -8 . Then the difference between their $4^{	ext {th }}$ terms is\

Professor PC Thomas Classes · Answer

(c):The first term of first A.P. $\left(a_{1}ight)=-1$ The first term of second A.P. $\left(b_{1}ight)=-8$\ Two A.P. have the same common difference, $d_{1}=d_{2}$\ Difference between their $4^{	ext {th }}$ term\ $=a_{1}+3 d_{1}-\left(b_{1}+3 d_{2}ight)=-1+3 d_{1}-(-8)-3 d_{1} \quad\left(\because d_{1}=d_{2}ight)$ 
$=-1+8=7$