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Find k if the following equations are consistent: kx +3y + 1 = 0, x + 2y + 1 = 0, x + y = 0 - Mathematics and Statistics

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Question

Find k if the following equations are consistent:

kx + 3y + 1 = 0, x + 2y + 1 = 0, x + y = 0

Sum

Solution

Given equations are
kx + 3y + 1 = 0,

x + 2y + 1 = 0,

x + y = 0, i.e., x + y + 0 = 0.

Since these equations are consistent,

`|("k", 3, 1),(1, 2, 1),(1, 1, 0")|` = 0

∴ k(0 – 1) – 3(0 – 1) + 1(1 – 2) = 0

∴ k(–1) – 3(–1) + 1(–1) = 0

∴ – k + 3 – 1 = 0

∴ k = 2

shaalaa.com
Application of Determinants - Consistency of Three Equations in Two Variables
  Is there an error in this question or solution?
Chapter 4: Determinants and Matrices - Exercise 4.3 [Page 75]

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