Q1 of 71 Page 58

Solve the following pairs of linear equations by the method of substitution:

x + y = 7, 3x — y = 1

x + y = 7

⇒ x = 7 – y …[1]


By substituting eq[1] in 3x – y = 1


⇒ 3(7 – y) – y = 1


⇒ 21 – 3y – y = 1


⇒ 4y = 20


⇒ y = 5


If we put the above result in eq[1], we get


⇒ x = 7 – 5


⇒ x = 2


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