Question

for an AP. if t4=20 and t7 =32 find a,d and tn
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Answer 1

Answer:

a=8 d=4 tn= 8 + (n-1)4

Step-by-step explanation:

WKT

tn= a1 + (n-1)d

So, t4= a1 + (4-1)d

~ t4= a1 + 3d

~ 20=a1 +3d ........(i)

And, t7= a1 + (7-1)d

~ t7= a1 + 6d

~ 32= a1 + 6d ........(ii)

Subtracting (i) from (ii) -

12 = 3d

~ d =4

Also, a = 20-3d = 8

Now, tn = 8 + (n-1)d

Cheers!