Question

The 7th term of A.P -4 and it's 13th term is -16 , Find the A.P

Answer 1

a7 = a + 6d
-4 = a + 6d --------- eqn1
a13 = a + 12d
-16 = a + 12d ----------- eqn2
Subtract eqn1 from 2
We get
a + 12d = -16
- a + 6d = -4
__________
6d = - 12
__________
d = -12/6
d = -2
By putting the value of d in eqn1
a = -4 + { 6 (-2)}
a = -4 -12
a = -16
a1 = a = -16
a2 = a + d = -16 - 2 = -18
a3 = a + 2d = -16 -4 = -20
a4 = a + 3d = -16 -6 = -22
AP -> -16, -18, -20, -22, ............

Answer 2

Answer:

$hey$

Step-by-step explanation:

a+6d=-4

a+12d=-16

Subtracting:

-6d=12

d=-2

a+6*(-2)=-4

a=8

a=8, d=-2