Tìm x 51162–(14015+x)=1111 (7654–x)–1008=2222 36:x=x 2tính 3 17/24+2 8/15+1 7/8 3 tính hợp lý 1/2+/6+1/12+1/20+1/30+1/42 1/3+1/15+1/35+1/63+1/99

0 bình luận về “Tìm x 51162–(14015+x)=1111 (7654–x)–1008=2222 36:x=x 2tính 3 17/24+2 8/15+1 7/8 3 tính hợp lý 1/2+/6+1/12+1/20+1/30+1/42 1/3+1/15+1/35+1/63+1/99”

1. Đáp án:

   Bài 1:

   51162 – (14015 + x) = 1111

                   14015 + x = 51162 – 1111

                   14015 + x = 50051

                                 x = 50051 – 14015

                                 x = 36035

                       Vậy x = 36035

   (7654 – x) – 1008 = 2222

                 7654 – x = 2222 + 1008

                 7654 – x = 3230

                             x = 7654 – 3230

                             x = 4424

                   Vậy x = 4424

     36  : x = x

          36 = x . x

          36 = x²

          6² = x²

   ⇒ x = 6

      Vậy x = 6

   Bài 2:

   `3“\frac{17}{24}` + `2“\frac{8}{15}`+`1“\frac{7}{8}`

   = `\frac{89}{24}` + `\frac{38}{15}`+ `\frac{15}{8}`

   = `\frac{445}{120}` + `\frac{304}{120}`+ `\frac{225}{120}`

   = `\frac{487}{60}`

   Bài 3:

   `\frac{1}{2}`+ `\frac{1}{6}` + `\frac{1}{12}` +`\frac{1}{20}`  +  `\frac{1}{30}` +`\frac{1}{42}`

   = `\frac{1}{1 . 2}`+ `\frac{1}{2.3}` + `\frac{1}{3.4}` + `\frac{1}{4.5}` +`\frac{1}{5.6}` +`\frac{1}{6.7}`

   = `1` – `\frac{1}{2}` + `\frac{1}{2}` – `\frac{1}{3}` + `\frac{1}{3}` – `\frac{1}{4}` + `\frac{1}{4}`-`\frac{1}{5}` + `\frac{1}{5}`- `\frac{1}{6}` + `\frac{1}{6}` – `\frac{1}{7}`

   = `1` – `\frac{1}{7}`

   = `\frac{6}{7}`

   `\frac{1}{3}`+ `\frac{1}{15}` + `\frac{1}{35}` +`\frac{1}{63}`  +  `\frac{1}{99}`

   = `\frac{1}{1.3}`+ `\frac{1}{3.5}` + `\frac{1}{5.7}` +`\frac{1}{7.9}`  +  `\frac{1}{9.11}` 

   = `1` – `\frac{1}{3}`+ `\frac{1}{3}` – `\frac{1}{5}` + `\frac{1}{5}` – `\frac{1}{7}` +`\frac{1}{7}` – `\frac{1}{9}` +  `\frac{1}{9}` – `\frac{1}{11}`

   = `1` – `\frac{1}{11}`

   = `\frac{10}{11}`

   Bình luận

2. Giải thích các bước giải: 

   `51162 – (14015 + x) = 1111`

   `⇒ 51162 – 14015 – x = 1111`

   `⇒ 37147 – x = 1111`

   `⇒ x = 37147 – 1111`

   `⇒ x = 36036`

   .

   `(7654 – x) – 1008 = 2222`

   `⇒ 7654 – x – 1008 = 2222`

   `⇒ -x = 2222 – 7654 + 1008`

   `⇒ -x = -4424`

   `⇒ x = 4424`

   .

   `36 : x = x`

   `⇒ x^2 = 36`

   `⇒ x = ± 6`

   Vậy `x= ± 6`

   .

   `3 17/24 + 2 8/15 + 1 7/8`

   `= 89/24 + 38/15 + 15/8`

   `= 445/120 + 304/120 + 225/120`

   `= 974/120 = 487/60`

   .

   `1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42`

   `= 1/1.2 + 1/2.3 + 1/3.4 + 1/4.5 + 1/5.6 + 1/6.7`

   `= 1 – 1/2 + 1/2 – 1/3 + 1/3 – 1/4 + 1/4 – 1/5 + 1/5 – 1/6 + 1/6 – 1/7`

   `= 1 – 1/7 = 6/7`

   .

   `1/3 + 1/15 + 1/35 + 1/63 + 1/99`

   `= 1/1.3 + 1/3.5 + 1/5.7 + 1/7.9 + 1/9.11`

   `= 1/2 . (2/1.3 + 2/3.5 + 2/5.7 + 2/7.9 + 2/9.11)`

   `= 1/2 . (1 – 1/3 + 1/3 – 1/5 + 1/5 – 1/7 + 1/7 – 1/9 + 1/9 -1/11)`

   `= 1/2 . (1 – 1/11)`

   `= 1/2 . 10/11 = 5/11`

   Bình luận