Question

Find the 20th term of the ap whose third term is 7 and seventeenth term exceeds 3 times the third term by 2.also find its nth term​

Answer 1

a3=7

a+2d=7...1)

a7=3(a3)+2

a+6d=3(7)+2

a+6d=23..(2)

a+2d=7

a+6d=23

-4d=-16

d=16/4

d=4

IF d=4 THEN a=

a+2d=7

a+2(4)=7

a+8=7

a=-1

a20=a+19d

=-1+19(4)

=-1+76

=75

SO, 25th term of an AP is 75

hope it's help u

Answer 2

Find the 20th term of the ap whose third term is 7 and seventeenth term exceeds 3 times the third term by 2. Also find its nth term

• a3 = 7
• a + 2d = 7 ...(1)

• a7 = 3(a3) + 2
• a + 6d = 3 × 7 + 2
• a + 6d = 23 ...(2)

Now subtract (1) from (2)

• (a + 6d = 23)-(a + 2d = 7)
• = 4d = 16

So,

• 4d = 16
• d = 16/4
• d = 4

Now replace d with 4 in (1)

• a + 2 × 4 = 7
• a + 8 = 7
• a = 7 -8
• a = -1

Now,

• a20
• = a + 19d
• = -1 + 19 × 4
• = 75

Then,

• an
• = a + (n - 1)d
• = -1 + (n - 1)4
• = -1 + 4n - 4
• = 4n - 5 ans