⇒" role="presentation" style="border:0px; direction:ltr; display:inline; float:none; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax">≥0" role="presentation" style="border:0px; direction:ltr; display:inline; float:none; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax">≥0 ⇒" role="presentation" style="border:0px; direction:ltr; display:inline; float:none; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax">a≤b≤c" role="presentation" style="border:0px; direction:ltr; display:inline; float:none; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax">a≤b≤c ≤" role="presentation" style="border:0px; direction:ltr; display:inline; float:none; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax">⇒" role="presentation" style="border:0px; direction:ltr; display:inline; float:none; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax">≤" role="presentation" style="border:0px; direction:ltr; display:inline; float:none; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax">a≤b" role="presentation" style="border:0px; direction:ltr; display:inline; float:none; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:0px; position:relative; white-space:nowrap; word-wrap:normal" class="MathJax">a≤ba2≤ab≤3" role="presentation" style="border:0px; direction:ltr; display:inline; float:none; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:0px; position:relative; white-space:nowrap; word-wrap:normal" class="MathJax">a2≤ab≤3⇒" role="presentation" style="border:0px; direction:ltr; display:inline; float:none; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:0px; position:relative; white-space:nowrap; word-wrap:normal" class="MathJax">⇔" role="presentation" style="border:0px; direction:ltr; display:inline; float:none; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax">0≤b−1≤c−1" role="presentation" style="border:0px; direction:ltr; display:inline; float:none; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax">0≤b−1≤c−1 nên b-1 = 1, c-1 =2 ⇒" role="presentation" style="border:0px; direction:ltr; display:inline; float:none; line-height:normal; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax">(a, b, c) = (0, 0, 0) , (1, 2 , 3) , (1, 3, 2), ( 2, 1, 3) , ( 2, 3, 1 ) , ( 3, 1, 2 ) , ( 3, 2, 1 )
Ghi dấu bé hơn hoặc bằng mà nó không hiện lên =))
TH1 : a.b.c = 0 thì a + b + c = 0 => a = b = c = 0
TH2 : Bài toán đưa về dạng: a + (a+1) + (a+2) = a * (a+1) * (a+2)
Khai triển 2 vế trên ta được 3a + 3 = a^3 + 3a^2 + 2a
Chuyển vế a^3 +3a^2 - a - 3 = 0 (a+3) (a^2-1) = 0
PT trên có 3 nghiệm a = 1 a = -1 a = -3
Vậy ta có các cặp: a = 1 -> 1, 2, 3: tổng = tích = 6 a= -1 -> -1, 0, 1: tổng = tích = 0 a= -3 -> -3, -2 , -1: tổng = tích = -6 Vì là số nguyên dương -> cả 3 số đều phải >=0
Vậy chọn 1,2,3
Vậy (a; b; c) \(\in\) {(0;0;0); (1;2;3)}
