Question

Help me to solve this question so that you will marked as brainlist thank you​

Answer 1

Answer:

Step-by-step explanation:

A= -4

20th term =53

N=20

Sum of n terms=n/2{a+an}

=20/2(-4+53)

= 10 ×49

= 490

Answer 2

Answer:

28)490    29)100   30)3n -10

Step-by-step explanation:

28)1st term = a , last term = l

       Sₙ = n/2 (a + l)

       S20 = 20/2 (-4 + 53) = 10×49 = 490

29)tₙ = a+(n-1)d

     t25 = 9+24×5 = 129

     t5 = 9+4×5 = 29

      ∴ t25 - t5 = 129 - 29 =100

30) tₙ = a+(n-1)d ⇒ -7 + (n-1) × 3 = -7 + 3n -3 = -10 +3n = 3n-10