Index does not working.

I created a table

CREATE TABLE my_table
(
  id int4 NOT NULL,
  name varchar(64) NOT NULL,
  deleted bool NOT NULL,
  active bool NOT NULL,
  CONSTRAINT my_table_pkey PRIMARY KEY (id)
)

and  index

CREATE INDEX my_table_index
  ON my_table
  USING btree
  (deleted, active);


there is two identical queries...

1) select * from my_table where active and deleted

and

2) select * from my_table where active = true and deleted = true

First query does not use index in contrast to two query.

Why?

Thanks.
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