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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

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