Giải giúp mình ba bài dưới dây với!
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AH
Akai Haruma
Giáo viên
16 tháng 5 2021
Lời giải:
Tổng độ dài ba sợi dây là:
$(12,2+10,4+17,4):2=20$ (m)
Độ dài sợi dây thứ ba là:
$20-12,2=7,8$ (m)
Độ dài sợi dây thứ nhất là:
$20-10,4=9,6$ (m)
Độ dài sợi dây thứ hai là:
$20-17,4=2,6$ (m)
NH
1
PP
1
8 tháng 12 2021
\(ĐK:x\ne\dfrac{1}{2};x\ne1;x\ne\dfrac{3}{2};x\ne2;x\ne\dfrac{5}{2}\\ PT\Leftrightarrow\dfrac{1}{\left(2x-1\right)\left(x-1\right)}+\dfrac{1}{\left(x-1\right)\left(3x-2\right)}+\dfrac{1}{\left(3x-2\right)\left(x-2\right)}+\dfrac{1}{\left(x-2\right)\left(5x-2\right)}=\dfrac{4}{21}\\ \Leftrightarrow2\left[\dfrac{\dfrac{1}{2}}{\left(x-\dfrac{1}{2}\right)\left(x-1\right)}+\dfrac{\dfrac{1}{2}}{\left(x-1\right)\left(x-\dfrac{3}{2}\right)}+\dfrac{\dfrac{1}{2}}{\left(x-\dfrac{3}{2}\right)\left(x-2\right)}+\dfrac{\dfrac{1}{2}}{\left(x-2\right)\left(x-\dfrac{5}{2}\right)}\right]=\dfrac{4}{21}\)
\(\Leftrightarrow\dfrac{1}{x-1}-\dfrac{1}{x-\dfrac{1}{2}}+\dfrac{1}{x-\dfrac{3}{2}}-\dfrac{1}{x-1}+\dfrac{1}{x-2}-\dfrac{1}{x-\dfrac{3}{2}}+\dfrac{1}{x-\dfrac{5}{2}}-\dfrac{1}{x-2}=\dfrac{2}{21}\\ \Leftrightarrow\dfrac{1}{x-1}-\dfrac{1}{x-\dfrac{5}{2}}=\dfrac{2}{21}\\ \Leftrightarrow\dfrac{x-\dfrac{5}{2}-x+1}{\left(x-1\right)\left(x-\dfrac{5}{2}\right)}=\dfrac{2}{21}\\ \Leftrightarrow\dfrac{-\dfrac{3}{2}}{x^2-\dfrac{7}{2}x+\dfrac{5}{2}}=\dfrac{2}{21}\\ \Leftrightarrow x^2-\dfrac{7}{2}x+\dfrac{5}{2}=-\dfrac{63}{4}\\ \Leftrightarrow4x^2-14x+10=-63\\ \Leftrightarrow4x^2-14x+73=0\\ \Leftrightarrow x\in\varnothing\)
H
14 tháng 1 2022
1. have waited
2. has written
3. has studied
4. has finished
5 haven't done
6. We don't go to school on Saturdays
7. They usually hold a party on New Year's Eve
8. I have seen this film already
9. Last night she came home between 10.30 and 11 o'clock
10. We are going to see the movie Dream City at 7.00 this evening
TP
14 tháng 1 2022
1 have waited
2 has written
3 has studied
4 has finished
5 haven't done
6 We don't go to school on Saturdays.
7 They usually hold a party in New Year's Eve.
8 I've seen this film already.
9 Last night, she came home between 10.30 and 11 o'clock.
10 We are going to see the movie Dream City at 7.00 this evening.
NH
2
NH
1
NH
2
H
26 tháng 12 2022
\(2x=3y\\ =>\dfrac{x}{3}=\dfrac{y}{2}\\ 4y=5z\\ =>\dfrac{y}{5}=\dfrac{z}{4}\\ \dfrac{x}{3}=\dfrac{y}{2}\\ =>\dfrac{x}{3.5}=\dfrac{y}{2.5}\\ =>\dfrac{x}{15}=\dfrac{y}{10}\\ \dfrac{y}{5}=\dfrac{z}{4}\\ =>\dfrac{y}{5.2}=\dfrac{z}{4.2}\\ =>\dfrac{y}{10}=\dfrac{z}{8}\\ =>\dfrac{x}{15}=\dfrac{y}{10}=\dfrac{z}{8}\)
Áp dụng tính chất dãy tỉ số bằng nhau
\(\dfrac{x}{15}=\dfrac{y}{10}=\dfrac{z}{8}=\dfrac{x+y+z}{15+10+8}=\dfrac{11}{33}=\dfrac{1}{3}\\ =>\left\{{}\begin{matrix}x=\dfrac{1}{3}.15=5\\y=\dfrac{1}{3}.10=\dfrac{10}{3}\\z=\dfrac{1}{3}.8=\dfrac{8}{3}\end{matrix}\right.\)
NH
2
H
26 tháng 12 2022
\(a,\dfrac{3^{10}.11+9^5.5}{27^3.2^4}.x=-9\\ =>\dfrac{3^{10}.11+\left(3^2\right)^5.5}{\left(3^3\right)^3.2^4}.x=-9\\ =>\dfrac{3^{10}.\left(11+5\right)}{3^9.2^4}.x=-9\\ =>\dfrac{3^{10}.16}{3^9.2^4}.x=-9\\ =>\dfrac{3^{10}.2^4}{3^9.2^4}.x=-9\\ =>3^1.x=-9\\ =>x=-9:3\\ =>x=-3\)
NH
2
H
26 tháng 12 2022
Giải
\(\sqrt{\dfrac{9}{4}}-\left|2x+1\right|=0,75\)
TH1: \(\left|2x+1\right|=2x+1\)
\(=>\sqrt{\dfrac{9}{4}}-\left(2x+1\right)=0,75\\ =>\dfrac{3}{2}-2x-1=\dfrac{3}{4}\\ =>\left(\dfrac{3}{2}-1\right)-2x=\dfrac{3}{4}\\ =>\dfrac{1}{2}-2x=\dfrac{3}{4}\\ =>2x=\dfrac{1}{2}-\dfrac{3}{4}\\ =>2x=-\dfrac{1}{4}\\ =>x=\left(-\dfrac{1}{4}\right):2\\ =>x=-\dfrac{1}{8}\)
\(TH2:\left|2x+1\right|=-2x-1\\ =>\sqrt{\dfrac{9}{4}}-\left(-2x-1\right)=\dfrac{3}{4}\\ =>\dfrac{3}{2}+2x+1=\dfrac{3}{4}\\ =>\left(\dfrac{3}{2}+1\right)+2x=\dfrac{3}{4}\\ =>\dfrac{5}{2}+2x=\dfrac{3}{4}\\ =>2x=\dfrac{3}{4}-\dfrac{5}{2}\\ =>2x=-\dfrac{7}{4}\\ =>x=\left(-\dfrac{7}{4}\right):2\\ =>x=-\dfrac{7}{8}\)