Rectangle that measures 4cm across 15cm down

Is the following relation a function? x y 1 4 −1 −2 3 10 5 16 yes no

International calls require the use of a country code. many country codes a 3-digit numbers. country codes do not begin with a 0 or 1. there are no restrictions on the second and third digits. how many different 3-digit country codes are possible?

Idon’t understand! use slope intercept form to solve: through: (2,5) slope= undefined