Question

find the 10th term of the AP - 15 - 11 - 7........,49​

Answer 1

Step-by-step explanation:

a=−11

d=4

49=−11+(n−1)4

60=4n−4

64=4n

n=16⟶ there are 16 terms.

Since the terms are even, there will be two middle most terms.

∴n=8,9

When n=8,a8=17, n=9, a=9 a9=21

∴a0,9= 17+21/ 2 =19

Answer 2

Given :

• AP => -15 , -11 , -7 .......49

To find :

• 10th term ( a{10} )

Formula used :

a{n} = a + (n-1)d

here ,

• a = first term
• a{n} = nth term
• d = common difference

Solution :

a{1} = -15

a{2} = -11

d = a{2} - a{1}

d = (-11) - (-15)

d = -11 + 15

d = 4

a{10} = a + (10-1)d

a{10} = (-15) + (9)(4)

a{10} = -15 + 36

a{10} = 21

ANSWER : a{10} = 21