Question

the 9th term of an arithmetic progression is -32 and the sum of its 11th and 13th term is -94. find the common difference of the arithmetic progression.

Answer 1

Answer:

a9=-32=a+8d=-32=2a+16d=-64----(i)

a11+a13=-94

a+10d+a+12d=-94

2a+22d=-94----(ii)

(ii)-(i)=6d=-30

d=-5

Answer 2

Answer:

-5

Step-by-step explanation:

9th term = a+(9-1)d = a+8d = -32--(2)

11th term = a+(11-1)d = a+10d

13th term = a+(13-1)d = a+12d

a+10d+a+12d=-94

2a+22d=-94

a+11d=-47---(1)

(2)-(1):

-3d=15

d=-5

the common difference is equal to -5