Exams

Here as given Q is in the middle and it satisfies all other conditions given in the question.

Graphite is a covalent-network type of crystalline solid.

There are two main categories of solids.

1. Crystalline solids and

2. Amorphous solids.

Crystalline solids are those in which the atoms, ions, or molecules that make up the solid exist in a regular, well-defined arrangement.

There are four types of crystalline solids :

Ionic solids :— Made up of positive and negative ions and held together by electrostatic attractions. They’re characterized by very high melting points and brittleness and are poor conductors in the solid state. An example of an ionic solid is table salt, NaCl.

Molecular solids :— Made up of atoms or molecules held together by London dispersion forces, dipole-dipole forces, or hydrogen bonds. Characterized by low melting points and flexibility and are poor conductors. An example of a molecular solid is sucrose.

Covalent-network (also called atomic) solids :— Made up of atoms connected by covalent bonds; the intermolecular forces are covalent bonds as well. Characterized as being very hard with very high melting points and being poor conductors. Examples of this type of solid are diamond and graphite, and the fullerenes. As you can see below, graphite has only 2-D hexagonal structure and therefore is not hard like diamond. The sheets of graphite are held together by only weak London forces!

Metallic solids :— Made up of metal atoms that are held together by metallic bonds. Characterized by high melting points, can range from soft and malleable to very hard, and are good conductors of electricity.

Since he is telling about the thing that had happened in past.

By trial and error method, when we substitute 

x = 0

Both LHS and RHS are equal.

C++ is not an Operating System.

An Operating System is a collection of system programs that manages all the other programs application programs in a computer as well as the allocation and use of hardware resources such as the CPU, Memory and the Hard Disk Drive.

It acts as an interface between the hardware and the user level program.

It controls and facilitates the overall operation of a computer. 

Here

UNIX : UNIX is a popular multi-user, multitasking operating system (OS) developed at Bell Labs.

Windows NT : Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993.

DOS : DOS is Disk Operating System. The term DOS can refer to any operating system.

C++ : C++ is a programming language and computing platform.

Hence, C++ is not an Operating System.

The series rtus/rtus/rtus/rtus. Thus, the pattern 'rtus' is repeated.

Given that 3x-y=27, 3x+y=243

⇒3x-y =33 , 3x+y=35

 => x-y=3, x+y=5

 => x = 4