Math, asked by AlnaVincent, 2 months ago

10th term of an arithmetic sequence is 30 and 20th term is 70 .find the common difference,and it's first term and also the sequence​

Answers

Answered by kv44489
4

Answer:

20th term - 10th term = 70 - 30

10 = 40

then, 1 = 40/10 = 4

The difference = 4

10th term = 30

30 ÷ 4

Quotient = 7 and remainder = 2

10th term = [ 4 × ( 10 - 3 ) ] + 2

=> [ 4 × 7 ] + 2

=> 28 + 2 = 30

it means the pattern of the number is

4 × ( term - 3 ) + 2

then, the first term

=> [ 4 × ( 1 - 3 ) ] + 2

=> [ 4 × (-2) ] + 2 )

=> (-8) + 2

=> -6

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Answered by Dhanushree24
0

as given

10th term of an AP is 30

and 20th term is 70

a10=30

a20=70

a10=a+9d eq 1

a20=a+19d eq2

eq2-eq1

substitute the values of a10 and a20 in both eq

a+19d=70

a+9d=30

then,

a+19d=70

-a-9d=-30

by simplifying we get

10d=40

d=40 divided by 10

d =4

substitute d=4 in eq 1

we get

a+9d=30

a+9×4=30

a+36=30

a= 30-36

a= -6

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