 # Linear equations in two Variables Chapter 4 Exercise 4.1

In this page we have NCERT book Solutions for Class 9th Maths Linear equations in two variables for EXERCISE 4.1 on page 68. Hope you like them and do not forget to like , social share and comment at the end of the page.
Question 1
The cost of a notebook is twice the cost of a pen. Write a linear equation in two variables to represent this statement.
(Take the cost of a notebook to be Rs x and that of a pen to be Rs y.)
Solution
Let cost of notebook and a pen be x and y respectively.
Cost of note book = 2 cost of pen
$x = 2y$
$x - 2 y = 0$

Question 2
Express the following linear equations in the form ax + by + c = 0 and indicate the values of a, b, c in each case:
(i) $2x+3y=9.3\bar{5}$
(ii) $x- \frac {y}{5}-10=0$
(iii) $-2x + 3 y = 6$
(iv) $x = 3y$
(v) $2x = - 5y$
(vi) $3x + 2 = 0$
(vii) $y - 2 = 0$
(viii) $5 = 2x$
Solution
(i) $2x+3y=9.3\bar{5}$
=> $2x+3y-9.3\bar{5} =0$
Comparing this equation with $ax + by + c = 0$,
a=2 ,b=3 $c=-9.3\bar{5}$.

(ii) $x- \frac {y}{5}-10=0$
Comparing this equation with $ax + by + c = 0$,
a = 1, b =-1/5,c = -10

(iii) $-2x + 3 y = 6$
=> $-2x + 3 y - 6 = 0$
Comparing this equation with $ax + by + c = 0$,
a = -2, b = 3, c = -6
(iv)$x = 3y$
=> $x - 3y + 0 = 0$
Comparing this equation with $ax + by + c = 0$,
a = 1, b = -3, c = 0
(v) $2x = - 5y$
=> $2x + 5y + 0= 0$
Comparing this equation with $ax + by + c = 0$,
a = 2, b = 5, c = 0
(vi) $3x + 2 = 0$
=> $3x + 0.y + 2 = 0$
Comparing this equation with $ax + by + c = 0$,
a = 3, b = 0, c = 2
(vii) $y - 2 = 0$
=> y - 2 = 0
Comparing this equation with $ax + by + c = 0$,
a = 0, b = 1, c = -2
(vii) $5 = 2x$
=> $- 2x + 5 = 0$
Comparing this equation with $ax + by + c = 0$,
a = -2, b = 0, c = 5

Reference Books for class 9 Math

Given below are the links of some of the reference books for class 9 Math.

1. Mathematics for Class 9 by R D Sharma One of the best book for studying class 9 level mathematics. It has lot of problems to be solved.
2. Secondary School Mathematics for Class 9 by R S Aggarwal This is also as good as R.D. Sharma. Either this or the book by R.D. Sharma will do. I find book R.S. Aggarwal little bit more challenging than the one by R.D. Sharma.
3. Pearson IIT Foundation Series - Maths - Class 9 Buy this book if you want to challenge yourself further and want to prepare for JEE foundation.
4. Pearson IIT Foundation Physics, Chemistry & Maths combo for Class 9 Only buy if you are prepared to study extra topics and want to take your studies a step further. You might need help to understand topics in these books.

You can use above books for extra knowledge and practicing different questions.

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