Final answer:
The line perpendicular to y=15 passing through (4, -9) is the vertical line with the equation x=4.
Step-by-step explanation:
To find the line perpendicular to y=15 and passing through the point (4, -9), we must first recognize that y=15 is a horizontal line. Therefore, a line perpendicular to it will be a vertical line, and the slope of a vertical line is undefined. A vertical line that passes through the point (4, -9) would have the equation x=4.For example, if a class C network is being used and each subnet needs to support at least 30 hosts, the subnet mask could be 255.255.255.224, which allows for 32 addresses (30 usable addresses plus network and broadcast address). For this scenario, the number of subnets would be determined by how many bits you borrow from the host part of the address to create these subnets.