NCERT Solutions for Class 9th Mathematics
Chapter 4. Linear Equation In Two Variables
Exercise 4.2
Chapter 4. Linear Equation In Two Variables
Exercise 4.2
1. Which one of the following options is true, and why?
y = 3x + 5 has
(i) a unique solution, (ii) only two solutions,
Solution
(iii) infinitely many solution, because we can put many value of x and can get many solution of y.
2. Write four solutions for each of the following equations:
(i) 2x + y = 7
(ii) πx + y = 9
(iii) x = 4y
Solution
3. Check which of the following are solutions of the equation x – 2y = 4 and which are not:
(i) (0, 2)
(ii) (2, 0)
(iii) (4, 0)
Solution :
x = 4 + 2y
(i) (0,2)
Putting value of x and y
= 0 = 4 + 2(2)
= 0 = 4 + 4 = 0 = 8, hence it is not a solution of eq
(ii) (2,0)
Putting value of x and y
= 2 = 4 + 2(0) = 2 = 4, hence it is also not a solution of eq
(iii) (4,0)
Putting value of x and y
= 4 = 4 + 2(0) = 4 = 4, hence it is a solution of eq
(v) (1,1)
Putting value of x and y
= 1 = 4 + 2(1) = 1= 6, hence, it is not a solution of eq
4. Find the value of k, if x = 2, y = 1 is a solution of the equation 2x + 3y = k.
Solution :
2x + 3y = k
Putting the value of x and y
2(2) + 3(1) = k = 4+3 = k = k = 7