tìm tất cả các số có 2 chữ số sao cho nó có thể biểu diễn bằng tổng các chữ số của nó cộng với tích các chữ số của nó. Các bạn giúp mình với nhá . thank các bạn
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địt lồn mẹ mày bú buồi đầu buồi liếm lông chim
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Mình biết đáp số rồi nhưng ko biết cách giải như thế nào ?
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Gọi số đó là abc ta có abc=a+b+c. Giả sử \(9\ge a\ge b\ge c\ge0\) thì \(abc=a+b+c\le3a\) suy ra \(bc\le3\)
abc khác 0 (vì \(a\ge1\) nên a+b+c\(\ge1\))
bc=3 thì b=3, c=1, suy ra 3+1+a=3a suy ra a=2 (loại, vì a bé hơn b)
bc=2 => b=2, c=1 suy ra 3+a=2a suy ra a=3 (Chọn)
bc=1 => b=1, c=1 suy ra 2+a=a (loại)
Vậy Các số cần tìm là 123, 132, 213, 231, 312, 321
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Gọi số có 2 chữ số càn tìm là ab
Ta có ab = a x b + a + b
=> 10 x a + b = a x b + a + b
=> 10 x a = a x b + a
=> 10 x a - a = a x b
=> 9 x a = a x b (1)
Vì a khác 0
=> b = 9
Khi đó (1) <=> 9 x a = a x 9
=> a thỏa mãn với mọi số tự nhiên a
mà \(0< a< 10\)
=> Các số tự nhiên có 2 chữ số cần tìm là 19 ; 29 ; 39 ; 49 ; 59 ; 69 ; 79 ; 89 ; 99
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số đó là 89 bởi vì:
89 = (8 x 9) +( 8 + 9) = 72 + 17 = 89
=> số đó là 89
bạn học lớp 6b k
T bắt quả tang con quỳnh lên mạng hỏi bài nhé