Question

For the AP :-3,-7,-11.., can we find a30-a20 without actually finding a30 and a20 ? Give reason

Answer 1

Answer:

Step-by-step explanation:

∵ nth term of an AP, an = a + (n-1)d

∴ a30 = a + (30 - 1)d = a + (30 - 1)d = a + 29d ...(i)

and a20 = a + (20 - 1)d = a + 19d

Now, a30 - a20 = (a + 29d) - (a+19d) = 10d

and from given AP common difference, d = -7-(-3) = -7+3

= -4

∴ a30 - a20 = 10(-4) = - 40