First AP
Given a = –1
We know that
an = a + (n – 1) d
So, 4th term will be
a4 = – 1 + (4 – 1) d
a4 = – 1 + 3d
So, 4th term of 1st AP = – 1 + 3d
Second AP
Given b = −8
We know that
bn = b + (n – 1) d
So, 4th term will be
b4 = – 8 + (4 – 1)d
b4 = – 8 + 3d
So, 4th term of 2nd AP = – 8 + 3d
,
So difference between their 4th terms
a4 – b4
= – 1 + 3d – (– 8 + 3d)
= – 1 + 3d + 8 – 3d
= 7
So, the correct answer is (c)
Made by
Davneet Singh
Davneet Singh is an IIT Kanpur graduate and has been teaching for 16+ years. At Teachoo, he breaks down Maths, Science and Computer Science into simple steps so students understand concepts deeply and score with confidence.
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