Question

plz answer in my question no 3

Answer 1

ʜᴇyyy ᴛʜᴇʀᴇ..
ᴜʀ ᴀɴꜱ ɪꜱ ʜᴇʀᴇ .

♥Sequence = An ordered collection of numbers a1 , a2 , a3 ,............
an......is a sequence.

♥Arithmetic progression = A sequence a1,a2,a3,.........,an is called an Arithmetic progression (A.P.) when a2-a1 = a3-a3 =......an -a(n-1) . That means A.P. is a sequence in which each term is obtained by addind a constant d to the preceding term.

♥d = The constant d is called common difference of the A.P .

♥FORMULAS -----
d= a2 - a1
an = a + (n-1 )d
sn = n/2 [2a +( n-1) d]
sn = n/2 ( a+ l)

where
a= first term of the A.P.
d = common difference
n = no of terms
an = nth term of A.p.
sn= sum to nth term
l = last term

Now come to ur Question-----

GIVEN ---
a = -11
d = 6
a21 = ???
S21 = ???
3×a3 + 4× a5 = ???


ᴡᴇ ᴋɴᴏᴡ ᴛʜᴀᴛ ----
an = a + ( n -1)d
so ,
a21 = (-11) + (21 -1 ) 6
= ( -11) + (20)6
= (-11) +120
= 109



wє knσw thαt ---
ѕn= n/2 ( α+l)
ѕσ,,,,,
ѕ21 = 21/2 [ (-11) + 109]
= 21/2 ( 98)
= 1029




N̤o̤w̤ ̤ f̤o̤r̤ 3×̤ a̤3̤ +̤ 4×̤ a̤5̤ w̤e̤ h̤a̤v̤e̤ t̤o̤ f̤i̤n̤d̤ a̤3̤ a̤n̤d̤ a̤5̤
̤
̤a̤n̤ =̤ a̤+̤ (̤n̤-̤1)̤d̤
̤
̤a̤3=̤ (-11)+(3-1)6
= (-11) +(2)6
= (-11) + 12
= 1

a5 = (-11) + (5-1)6
= (-11) + (4)6
=(-11) + 24
= 13


= 3× a3 + 4× a5
= 3 × (1) + 4 × 13
= 3 + 52
= 55




̤ ❤ʜᴏᴩᴇ ɪᴛ ʜᴇʟᴩꜱ ᴜ ❤
☺ꜰᴇᴇʟ ꜰʀᴇᴇ ᴛᴏ ᴀꜱᴋ ᴀɴy qᴜᴇʀy☺