1) 3+3а при a=(1/3)и a=-3
• 3 + 3 × 1/3 = 3 + 1 = 4
• 3 + 3 × (-3) = 3 - 9 = (-6)
4 > -6
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2) 1/7+1/2 > 1/3 + 1/5
• 1/7 + 1/2 = 9/14
• 1/3 + 1/5 = 8/15
9/14 > 8/15
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3) 0,4 > 1/3 -1/5
• 1/3 - 1/5 = 2/15
• 4/10 > 2/15