Class 9 Maths


Exercise 2.1 Part 1

Question 1: Which of the following expressions are polynomials in one variable and which are not? State reasons for your answer.

(i) `4x^2 -3x + 7`

Answer: Since, the given expression has only one variable ‘x’, hence this is a polynomial in one variable.

(ii) `y^2 + sqrt2`

Answer: Since, the given expression has only one variable ‘y’, hence this is a polynomial in one variable.

(iii) `3sqrt\t + t\sqrt2`

Answer: Since, variable, ‘t’ in this expression exponent of variable is not a whole number. [Exponent of a variable in a polynomial must be a whole number. Expression with exponent of a variable in fraction is not considered as a polynomial.]

(iv) `y + 2/y`

Answer: Since, exponent of the variable is negative integer, and not a whole number, hence it cannot be considered a polynomial.

(v) `x^10 + y^3 + t^50`

Answer: Since, given expression has three variables, i.e. x, y and t, so it is not a polynomial in one variable.

Question 2: Write the coefficients of x2 in each of the following:

(i) `2 + x^2 + x`

Answer: Given; `2 + x^2 + x`
Here, coefficient of `x^2 = 1`

(ii) `2 – x^2 + x^3`

Answer: Here, coefficient of `x^2 = 1`

(iii) `(π)/(2)\x^2 + x`

Answer: Here, coefficient of `x^2 = π/2`

(iv) `sqrt2x – 1`

Answer: Here, coefficient of `x^2 = 0`

Number System

Numbers are in the form of p/q or can be written in the form of p/q are called rational numbers.


Algebraic expression with many terms having variables and coefficients is called polynomial.

Coordinate Geometry

The distance of a point from the y - axis is called its x-coordinate, or abscissa, and the distance of the point from the x-axis is called its y-coordinate, or ordinate.

Linear Equations in Two Variables

A linear equation in two variables has infinite number of solutions.

Euclid's Geometry

The basic concept about a line is that it should be straight and that it should extend indefinitely in both the directions.

Lines & Angles

An angle is formed by two rays originating from the same end point. The rays making an angle are called the arms of the angle and the end-points are called the vertex of the angle.


Two figures are congruent, if they are of the same shape and of the same size. Two circles of the same radii are congruent. Two squares of the same sides are congruent.


Sum of the angles of a quadrilateral is 360°. A diagonal of a parallelogram divides it into two congruent triangles.


In a parallelogram: opposite sides are equal, opposite angles are equal, and diagonals bisect each other


The collection of all the points in a plane, which are at a fixed distance from a fixed point in the plane, is called a circle.

Heron's Formula

Heron's formula is generally used for calculating area of scalene triangle.

Surface Area

How to calculate surface area of cylinder, cone and sphere?


How to calculate volume of cylinder, cone and sphere?


Learn to make bar chart and histogram from given data.


Probability tells about likelihood of an event to occur.