Question

in an AP given a3=21,S10=255,find d and a10​

Answer 1

Answer:

a3=21,S10=255,find d and a10​

an=a+(n-1)d

a3=a+2d=21   (eq1)*2

42=2a+4d

sn=n/2(2a+(n-1)d)

255=10/2(2a+9d)

51=2a+9d       eq  2

eq(2-1)

51=2a+9d    

-42=-2a-4d

-----------------

9=5d

d=9/5 sub in 1

21=a+18/5

105=5a+18

87/5=a

a10=a+9d

=87/5+9*(9/5)

=168/5

Step-by-step explanation:

Answer 2

Answer:

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