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NCERT Class XI Mathematics - Linear Inequalities - Solutions
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Question : 39 of 65
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2x + y ≥ 6, 3x + 4y ≤ 12
Solution:
The inequalities are 2x + y ≥ 6, 3x + 4y ≤ 12 (i) The line l1 : 2x + y = 6 passes through (3, 0), (0, 6) AB represents the line 2x + y = 6 Putting x = 0, y = 0 in 2x + y ≥ 6 0 ≥ 6, which is false. ∴ Origin does not lie in the region of 2x + y ≥ 6 Therefore, the region lying above the line AB and all the points on AB represents the inequality 2x + y ≥ 6 (ii) The line l2 : 3x + 4y = 12 passes through (4, 0) and (0, 3). This line is represented by CD. Consider the inequality 3x + 4y ≤ 12 Putting x = 0, y = 0 in 3x + 4y ≤ 12, we get 0 ≤ 12, which is true. ∴ 3x + 4y ≤ 12 represents the region below the line CD (towards origin) and all the points lying on it. The common region is the solution of 2x + 3y ≥ 6 are 3x + 4y ≤ 12 represented by the shaded region in the graph.

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