# NCERT Class 9 Solution: Linear Equation In Two Variables (Chapter 4) Exercise 4.1

Q-1 The cost of a notebook is twice the cost of a pen. Write a linear equation in two variable to represent this statement.

(Take the cost of a notebook to be Rs and that of a pen to be Rs )

Solution:

Consider the cost of a notebook be and that of a pen be .

A linear equation has to equate the two things. According to question, the cost of a notebook is twice the cost of a pen

So,

Therefore, linear equation becomes,

.

Q-2 Express the following linear equations in the form and indicate the value of in each case:

Solution:

• So,

• Compare, the equation with

• Therefore, value of and is

• Compare the equation with .

• Therefore, .

• So,

• Compare, the equation with

• Therefore,

• So,

• Compare, the equation with

• Therefore,

• So,

• Compare, the equation with

• Therefore,

• Compare, the equation with

• Therefore,

• Compare, the equation with

• Therefore,

• So,

• Compare, the equation of

• Therefore,

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