Step-by-step explanation:

Sn = 5n -72

put n=1

S1 = 5 - 72

S1 = -67 , a = t1 = -67

put, n = 2

S2 = 10 -72

S2 = -62

t2 = S2 -S1

t2 = -62-(-67)

t2 = -62+67

t2 = 5

d = t2 - t1

d = 5 - (-67)

d = 5 + 67

d = 72

tn = a + (n-1)d

tn = -67 + (n-1)72

tn = -67 + 72n -72

tn = 72n - 139

Hope it's correct...

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