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Class- XI-CBSE- Linear equations in two variables
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Back of Chapter Questions
Exercise:
4 .1 1.T he cost of a notebook is twice the cost of pen write a linear equation in two variables to represent this statement.
Solution:
Let the cost of a notebook be
Given that cost of a notebook
= 2× cost of a pen Hence, xെ2y= 0 is the representation of the given statement.
2.Express the following linear equations in the form
ax+by+ c= 0 and indicate the values of a,b and c in each case:
F10= 0(iii)െ2x+3y= 6
(iv)x =3y (v)2x=െ5y (vi)3x+ 2= 0 (vii)yെ2 =0 (viii)5 =2x
Solution:
Comparing above equation with
ax+by+ c= 0. (ii)xെ
F10= 0
Comparing above equation with
ax+by+ c= 0. Class- XI-CBSE-Science Linear equations in two variables
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We get, a =1 ,b=െ
,c= െ10 (iii) െ2x+3y= 6
Comparing above equation with
ax+by+ c= 0.
We get, a =െ2,b=3 ,c =െ6
(iv) x =3y
Comparing above equation with
ax+by+ c= 0.
We get, a =1 ,b=െ3,c=0
(v) 2x=െ5y
Comparing above equation with
ax+by+ c= 0.
We get, a =2 ,b=5,c =0
(vi)
3x+ 2= 0
Comparing above equation with
ax+by+ c= 0.
We get, a =3 ,b=0,c =2
(vii) yെ2 =0
Comparing above equation with
ax+by+ c= 0.
We get, a =0 ,b=1,c =െ2
(viii) 5 =2x
Comparing above equation with
ax+by+ c= 0.
We get, a =െ2,b=0 ,c =5
Exercise: 4.2
1. Which one of the following options is true, and why? y =3x+ 5 has (i) a unique solution Class- XI-CBSE-Science Linear equations in two variables
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(ii) only two solutions (iii) infinitely many solutions
Solution:
(iii) is correct y =3x+ 5 has infinitely many solutions
For every xא
Hence infinitely many solutions.
2. Write four solutions for each of the following equations (i)
2x+ y= 7
(ii) Ɏx +y =9 (iii) x =4y
Solution:
(i)
2x+ y= 7
y =7 െ2x
For x =0
(0,7) is a solution.
For x =1
(1,5) is a solution.
For x =2
(2,3) is a solution.
For x =3
(3,1) is a solution. (ii) Ɏx +y =9
For x =
Class- XI-CBSE-Science Linear equations in two variables
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Ɏ= 8
,8ቁ is a solution
For x =
= 7 ,7ቁ is a solution
For x =
= 6 ,6ቁ is a solution
For x =0
(0,9) is a solution (iii) x =4y 4
For x =0
4 = 0
For x =4
= 1
For x =8
= 2
For x =12
Class- XI-CBSE-Science Linear equations in two variables
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4= 3 3. Check which of the following are solutions of the equation xെ2y= 4 and which are not (i) (0,2) (ii) (2,0) (iii) (4,0) (iv) ൫ξ2,4ξ2൯ (v) (1,1)
Solution:
(i) L.H.S xെ2y
Given point
(0,2) Hence (0,2) is not a solution of xെ2y= 4. (ii) L.H.S xെ2y
Given point
(2,0) Hence (2,0) is not a solution of xെ2y= 4. (iii) L.H.S xെ2y
Given point
(4,0) Class- XI-CBSE-Science Linear equations in two variables
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Hence (4,0) is a solution of xെ2y= 4. (iv) L.H.S xെ2y
Given point
൫ξ2,4ξ2൯ Hence , ൫ξ2,4ξ2൯ is a solution of xെ2y= 4. (v) L.H.S xെ2y
Given point
(1,1) Hence (1,1) is not a solution of xെ2y= 4. 4. Find the value of k, if x =2 , y =10 is a solution of the equation 2x+3y= k.
Solution:
Given that
(2,1) is a solution of the equation 2x+3y= k Therefore, if x =2 ,y=1 is a solution of equation 2x+3y= k, then k =7 .
Exercise: 4.3
1. Draw the graph of each of the following linear equations in two variables: (i) x +y =4 (ii) xെy =2 (iii) y =3x (iv)
3 =2x+ y
Solution:Given equation, x +y =4
Class- XI-CBSE-Science Linear equations in two variables
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At x =0 and x =4 we get y =4 and y =0 respectively.
Given equation, xെy =2
At y =0 and y =2 we get x =2 and x =0 respectively. Class- XI-CBSE-Science Linear equations in two variables
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Given equation, y =3x.
At x =0 we get y =0 Similarly, at x =1 and x =2 we get y =3 and y =6 respectively. (0,0),(1,3) and (2,6) are the solutions of y =3x. Class- XI-CBSE-Science Linear equations in two variables
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(iv)
Given equation, 3 =2x+ y.
At x =0 and x = we get y =3 and y =0 respectively. ,0ቁ are solutions of 3 =2x+ y. Class- XI-CBSE-Science Linear equations in two variables
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2.
Give the equations of two lines passing through
(2,14). How many more such lines are there, and why?
Solution:
Given point
(2,14)
Let x =2 and y =14
We can write 14= 7× 2
Similarly, 14= 2+ 12
From above process
we can say that there are different possible combinations of lines which passing through (2,14). Therefore, from a given point (2,14), there are infinite lines passing through it. 3.
If the point
(3,4) lies on the graph of the equation 3y=ax+ 7, find the value of a.
Solution:
Class- XI-CBSE-Science Linear equations in two variables
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Given that point (3,4) lies on graph of the equation 3y=ax+ 7 3 Therefore, if (3,4) is the solution of equation 3y=ax+ 7 then a = 4. total fare as
Solution:
Given
Total distance covered = x km
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[PDF] CBSE NCERT Solutions for Class 9 Mathematics Chapter 4