NCERT Class XI Mathematics - Linear Inequalities - Solutions

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Question : 38
Total: 65
3x + 2y ≤ 12, x ≥ 1, y ≥ 2
Solution:  

Inequalities are 3x + 2y ≤ 12, x ≥ 1, y ≥ 2
(i) The line l1 : 3x + 2y = 12 passes
through (4, 0), (0, 6)
AB represents the line, 3x + 2y = 12.
Consider the inequality 3x + 2y ≤ 12
Putting x = 0, y = 0 in 3x + 2y ≤ 12
0 + 0 ≤ 12, which is true.
Therefore, origin lies in the region
3x + 2y ≤ 12
∴ The region lying below the line AB including all the points lying on it.
(ii) The line l2 : x = 1 passes through (1, 0). This line is represented by EF. Consider the inequality x ≥ 1
Putting x = 0, 0 ≥ 1, which is not true.
Therefore, origin does not lie in the region of x ≥ 1
The region lies on the right of EF and the points on EF from the inequality x ≥ 1.
(iii) The line l3 : y = 2 passes through (0, 2). This line is represented by CD.
Consider the inequality y ≥ 2
Putting y = 0 in y ≥ 2, we get 0 ≥ 2 which is false.
∴ Origin does not lie in the region of y ≥ 2
y ≥ 2 is represented by the region above CD and all the points on this line.
Hence, the region satisfying the inequalities.
3x + 2y ≥ 12, x ≥ 1, y ≥ 2 is the ΔPQR.
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