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Pertidaksamaan

x y = 36
y = 36/x
Keliling pagar ≤ 43
3x + 4y ≤ 43
3x + 4(36)/x  ≤ 43
3x + 144/x ≤ 43
3x² - 43x + 144 ≤ 0
(3x -16)(x - 9) ≤ 0
x ≥ 16/3   atau x ≤ - 9