please answer this question
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Answer:
a=1,d=2
Step-by-step explanation:
s9= 81
s20= 400
s9= 9/2*(2a+8d)
81= 9/2*(2a+8d)
18=2a+8d
2a+8d=18----eq1
s20= 20/2*(2a+19d)
400=10(2a+19d)
2a+19d= 40---eq2
sub eq1 from 2
2a+19d-2a-8d=40-18
11d= 22
d= 22/11=2
2a+8*2=18
2a+16=18
2a=2
a=1
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