Question

The 6th term of an ap is -10 and its 10th term is -26 determine the 15th term of an ap

Answer 1

Answer

The 15th term of an ap is -46

Step-by-step explanation:

T6 = -10,T10 = -26,T15 = ?

Tn = a+(n-1)d

T6 = a+(6-1)d

-10 = a+5d..........(1)

T10 = a+(10-1)d

-26 = a+9d.........(2)

Take,(2)-(1)

-26 = a+9d

-10 = a+5d

__________

-16 = 4d

d = -16/4

d = -4

put value of d in equation (1)

-10 = a+5d

-10 = a+5×(-4)

-10 = a-20

-10+20 = a

a = 10

now,

T15 = a+(15-1)d

T15 = 10+14(-4)

T15 = 10-56

T15 = -46