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Question 2 The value of k for which the system of equations 3𝑥−𝑘𝑦=7 and 6𝑥+10𝑦=3 is inconsistent, is (A) – 10 (B) -5 (C) 5 (D) 7Since the system of equations is inconsistent It has no solution Finding ratios 𝟑𝒙−𝒌𝒚−𝟕=𝟎 Comparing with a1x + b1y + c1 = 0 ∴ a1 = 3 , b1 = −k , c1 = −7 𝟔𝒙+𝟏𝟎𝒚−𝟑=𝟎 Comparing with a2x + b2y + c2 = 0 ∴ a2 = 6 , b2 = 10, c2 = −3 𝒂𝟏/𝒂𝟐 𝑎1/𝑎2 = 3/6 𝑎1/𝑎2 = 1/2 𝒃𝟏/𝒃𝟐 𝑏1/𝑏2 = (−𝑘)/10 𝒄𝟏/𝒄𝟐 𝑐1/𝑐2 = (−7)/(−3) 𝑐1/𝑐2 = 7/3 Since the equations don’t have a solution 𝑎1/𝑎2 = 𝑏1/𝑏2 ≠ 𝑐1/𝑐2 1/2=(−𝑘)/10≠7/3 Thus, 1/2=(−𝑘)/10 10/2=−𝑘 5 = −k −5 = k k = −5 So, the correct answer is (B)

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.