Question

The ninth term of an A.P is - 32 and the sum of its eleventh and thirteenth term is - 94. Find the common difference of the A.P .

Answer 1

Answer:

Step-by-step explanation:

Let the first term be a and common diference be d.

Ninth term=    a+8d= -32........(i)

Sum of 11th and 13th term is -94 ∴  a+10d+a+12d=-94

                                                     or,2a+22d=-94

                                                     or,a+11d=-47..........(ii)

(ii) - (i) ⇒a + 11d - a - 8d = -47 + 32

⇒3d = -15

⇒d = -5

∴common difference = -5

Answer 2

nth term=a + (n-1)d
therefore, n11=a + 10d
n13=a + 12d