Answer with Step-by-step explanation:
Let F be a field .Suppose
and 
We have to prove that a has unique multiplicative inverse.
Suppose a has two inverses b and c
Then,
where 1 =Multiplicative identity

(cancel a on both sides)
Hence, a has unique multiplicative inverse.
<h3>Solution :</h3>
Distance between first tree and last tree is 140m .
And distance between each tree (d) = 5 m
let's solve for number of trees (n) :





hence, total number of trees = 29.
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