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Answer the following question: Find the value of k if the following equation are consistent: (k − 2)x +(k − 1)y =17 , (k − 1)x + (k − 2)y = 18 and x + y = 5 - Mathematics and Statistics

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Question

Answer the following question:

Find the value of k if the following equation are consistent:

(k − 2)x + (k − 1)y = 17 , (k − 1)x + (k − 2)y = 18 and x + y = 5

Sum

Solution

Since the given equations are consistent,

`|("k" - 2, "k" - 1, 17),("k" - 1, "k" - 2, 18),(1, 1, 5)|` = 0

By R2 – R1, we get,

`|("k" - 2, "k" - 1, 17),(1, -1, 1),(1, 1, 5)|` = 0

By C2 – C1, we get,

`|("k" - 2, 1, 17),(1, -2, 1),(1, 0, 5)|` = 0

∴ (k – 2)( –10 – 0) – 1(5 – 1) + 17(0 + 2) = 0

∴ - 10k + 20 – 4 + 34 =0

∴ -10k = – 50

∴ k = 5.

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Application of Determinants - Consistency of Three Equations in Two Variables
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Chapter 4: Determinants and Matrices - Miscellaneous Exercise 4(A) [Page 77]

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Balbharati Mathematics and Statistics 1 (Arts and Science) [English] 11 Standard Maharashtra State Board
Chapter 4 Determinants and Matrices
Miscellaneous Exercise 4(A) | Q II. (10) (iii) | Page 77
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