Discussion

Explanation:

5m + 7n = 11         ...(1)

7m + 5n = 1         ...(2)

Adding equations (1) and (2) we get,  

12m + 12n = 12

∴ m + n = 1              ...(3)

Subtracting equation (1) from equation (2) we get,

2m − 2n = −10

∴ m − n = − 5           ...(4)

Solving equation (3) and equation (4) we get, 

m = −2 and n = 3  

Alternately,

(1) × 7 – (2) × 5, we get

24n = 72

⇒ n = 3

Substituting value of n in 1st equation, we get m = -2.

Hence, option (d).

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