Answer:
The vertex is (-3,-2)
The vertex is basically the very top or very lowest, so you will notice how values around (-3,-2) are relatively the same in the y coordinate, but -2 is the "highest/lowest" so that's how you know it's a vertex.
If you try picturing the points in your head, you will see it make a U and at the bottom of the U is the vertex.
Answer:
An echo is formed as a result of reflection of the original sound which returns to the listener. You might have experienced Echo in an EMPTY ROOM but no echo is produced after the room is occupied. To avoid echo from being produced the echo has to be absorbed. Echo in a cinema theatre is absorbed by the WALLS of the theatre.
They are not plain. The walls are corrugated or shaped to form tiny holes or empty spaces to ABSORB the ECHO. Modern Theatre's have ABSORBENT materials sticked to the walls of the theatre.
