If [1 2 2 1]  [x  y] = [5 4] , then value of y is _______

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Question 13 If [1 2 2 1] [x y] = [5 4] , then value of y is _______ [1 2 2 1] [x y] = [5 4] [1 x + 2 y 2 x + 1 x y ] = [ 5 4] [ x + 2y 2x + y ] [ 5 4 ] Therefore, x + 2y = 5 2x + y = 4 …(1) …(2) Now solving (1) and (2), Doing (2) – 2 × (1) (2x + y) – 2 × (x + 2y) = 4 – 2 × 5 2x + y – 2x – 4y = 4 – 10 y – 4y = –6 –3y = –6 y = (−6)/(−3) y = 2 So, value of y is 2

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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.