Question 1

Solve the following pair of linear equations by the substitution method.

Answer

(i) x + y = 14 …………….(1)

x – y = 4 …………….(2)

From the equation (1), we get

x = 14 - y …………….(3)

Putting the value of x in equation (2), we get

(14 - y) – y = 4

14 – y – y = 4

- 2y = - 10

Putting the value of y in equation (3),

x = 14 – 5

x = 9

Hence, x = 9 and y = 5

(iii) 3x - y = 3 …………….(1)

9x – 3y = 9…………….(2)

From the equation (1), we get

Putting the value of y in equation (2), we get

9x – 3 (3x - 3) = 9

9x – 9x + 9 = 9

9 = 9, which is true.

Therefore, pair of linear equation has infinite many solutions.

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- NCERT Chapter