Question

two APs have same commanly difference the frist term of one of these is -1 and that of the other is -8 what is difference thier 4th term

Answer 1

Answer:

As I solved it,it would be 7 or -7.

Step-by-step explanation:

There are two AP's in which one of the first term is 1 and other is 8.

So let T1 be 8 and another term t1 be 1.

Let we take fourth term of the AP with T = 8

=) T4 = T1 + (n-1)*d

=) T4 = 8 + (n-1)*d

=) T4 = 8 + nd - d.

Now, take the another AP;

=) t4 = t1 + (n-1)d

=) t4 = 1 + nd - d.

∴ their difference would be;

=) T4-t4 = 8 + nd - d - (1 + nd - d)

              = 8 + nd - d - 1 - nd + d

              = 8 - 1. (nd - nd - d + d)

              = 7.

And if we do t4 - T4, the answer would be -7.

∴ the answer could be 7 or -7.