Question

please answer this question ​

Answer 1

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