Question

The 7th term of an AP is -4 and its 13th term is -16. Find the AP.
Plz answer the question

Answer 1

SOLUTION

The 7th term of an AP is

=) a+d(n-1)

for the 7th term,

=) a+d(7-1)= -4

=) a+ 7d- d= -4

=) a+ 6d= -4................(1)

for the 13th term,

=) a+ d(n-1) = 16

=) a+ d(13-1)= 16

=) a+ 13d- d= 16

=) a+ 12d= 16..............(2)

Subtract Equation (1) from (2)

=) a+12d= 16

=) a+ 6d= -4

- - +

______________

=) 6d= 20

=)d= 20/6

=) d= 10/3

Putting in we Equation (1)

=) a+6d= -4

=) a+6× 10/3= -4

=) a+20= -4

=) a=-4-24

=) a= -24

So, a= -24 and d= 10/3

So, AP is

=) -24, 62/3, 24, 82/3.....

HOPE it helps

Answer 2

Answer:

Step-by-step explanation:

T7=-4 =a+6d=-4.................(1)

T13=-16 = a+12d..............(2)

On subtracting (2)from (1) we get

6d=(-16-(-4) )

6d=(-16-+4 )

6d=(-12)

d=-2

So,

a+6×(-2)=-4

a+(-12)=-4

a=12-4

a=8

So,

T1=8

T2=a+d =8+(-2)=8-2 =6

T3=a+2d=8+(-2×2)=8-4=4

So,AP is 8,6,4,........