Tìm số nguyên x biết :
\(14\times7^{2021}=35\times7^{2021}-3\times49^{x}\)
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Ta có: \(\left(x-5\right)^7=\left(x-5\right)^9\)
=>\(\left(x-5\right)^9-\left(x-5\right)^7=0\)
=>\(\left(x-5\right)^7\cdot\left\lbrack\left(x-5\right)^2-1\right\rbrack=0\)
=>\(\left(x-5\right)^7\cdot\left(x-5-1\right)\left(x-5+1\right)=0\)
=>\(\left[\begin{array}{l}x-5=0\\ \left(x-5\right)=1\\ x-5=-1\end{array}\right.\Rightarrow\left[\begin{array}{l}x=5\\ x=6\\ x=4\end{array}\right.\)
1. ✔
2. ✘ ➞ What about getting a cleaner to wash your clothes?
3. ✘ ➞ I don't like ironing, so I have a woman do it for me.
4. ✔
5. ✘ ➞ Why haven't you had your films developed yet?
1 to cut => cut
2 wash => to wash
3 to do => do
4 đúng
5 develop => developed
1. ✔
2. ✘ ➜ Have you had a meal prepared for you?
3. ✘ ➜ We are having the trees in the garden cut down.
4. ✘ ➜ Ron is going to have his house repainted after the summer vacation.
5. ✘ ➜ When are you going to have the curtain washed?
1 đúng
2 prepare => prepared
3 cutting => cut
4 repainted his house => his house repainted
5 wash => washed
1. ✔
2. ✘ ➜ Have you had a meal prepared for you?
3. ✘ ➜ We are having the trees in the garden cut down.
4. ✘ ➜ Ron is going to have his house repainted after the summer vacation.
5. ✘ ➜ When are you going to have the curtain washed?
1 đúng 2 prepare => prepared 3 cutting => cut 4 repainted his house => his house repainted 5 wash => washed
lần đầu bán, còn lại : 31 . 0,5 - 0,5 = 15 ( kg )
lần hai bán, còn lại : 15 . 0,5 - 0,5 = 7 ( kg )
vậy lần ba bán 7 kg
Gọi số trừ là x (x ∈ N*)
Theo đề ra ta có : x 3 – x = 57
=>10x + 3 – x = 57
=>9x = 54 => x = 6
Vậy hai số cần tìm là 63 và 6
Mình đang thấy hơi lạ là thi KET là thi lên trình độ A2 đó. Mà bạn đang lớp 8 mà. Mình không có bí quyết gì nhưng bạn cứ lên mạng tra để hiểu thêm cấu trúc đề thi và căn chỉnh thời gian cho phù hợp nhé! Chúc bạn thành công.
14 x 7\(^{2021}\) = 35 x 7\(^{2021}\) - 3 x \(49^{x}\)
3 x 49\(^{x}\) = 35 x 7 \(^{2021}\) - 14 x \(7^{2021}\)
3 x 49\(^{x}\) = 7\(^{2021}\) x (35 - 14)
3 x 49\(^{x}\) = 7\(^{2021}\) x 21
49\(^{x}\) = 7\(^{2021}\) x 21 : 3
49\(^{x}\) = 7\(^{2021}\) x (21 : 3)
49\(^{x}\) = 7\(^{2021}\) x 7
49\(^{x}\) = 7\(^{2022}\)
(7\(^2\))\(^{x}\) = 7\(^{2022}\)
7\(^{2x}\) = 7\(^{2022}\)
2\(x\) = 2022
\(x\) = 2022 : 2
\(x\) = 1011
Vậy \(x=1011\)