Mọi người giúp mik với ! T-T
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
There is......... girl in my class.
A. not B. no C. aren't D. isn't
đây bài này ạ
mình gửi mà quên đăng ảnh. xloi bạn nha
11)\(\dfrac{3x+1}{x-5}+\dfrac{2x}{x-5}=\dfrac{3x+2x+1}{x-5}=\dfrac{5x+1}{x-5}\)
12)\(\dfrac{4-x^2}{x-3}+\dfrac{2}{x^2-9}=\dfrac{4-x^2}{x-3}+\dfrac{2}{\left(x-3\right)\left(x+3\right)}=\dfrac{\left(4-x^2\right)\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}+\dfrac{2}{\left(x-3\right)\left(x+3\right)}=\dfrac{2+\left(2-x\right)\left(2+x\right)\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}\)
13)
\(\dfrac{3}{4x-2}+\dfrac{2x}{4x^2-1}=\dfrac{3}{2\left(2x-1\right)}+\dfrac{2x}{\left(2x-1\right)\left(2x+1\right)}=\dfrac{3\left(2x+1\right)}{2\left(2x-1\right)\left(2x+1\right)}+\dfrac{2.2x}{2\left(2x-1\right)\left(2x+1\right)}=\dfrac{6x+3+4x}{2\left(2x-1\right)\left(2x+1\right)}=\dfrac{10x+3}{2\left(2x-1\right)\left(2x+1\right)}\)
14)
\(\dfrac{2x+1}{2x-4}+\dfrac{5}{x^2-4}=\dfrac{2x+1}{2\left(x-2\right)}+\dfrac{5}{\left(x-2\right)\left(x+2\right)}=\dfrac{\left(2x+1\right)\left(x+2\right)}{2\left(x-2\right)\left(x+2\right)}+\dfrac{5.2}{2\left(x-2\right)\left(x+2\right)}=\dfrac{2x^2+5x+12}{2\left(x-2\right)\left(x+2\right)}\)
Ta có:
\(C=\dfrac{2n-3}{n-2}=\dfrac{2n-4+1}{n-2}=2+\dfrac{1}{n-2}\)
\(C\in Z\Leftrightarrow\dfrac{1}{n-2}\in Z\Leftrightarrow n-2\inƯ\left(1\right)=\left\{-1;1\right\}\)
\(\Rightarrow...\)
Answer:
\(P=\frac{1}{1+x+xy+xyz}+\frac{1}{1+y+yz+yzt}+\frac{1}{1+z+zt+ztx}+\frac{1}{1+t+tx+txy}\)
\(=\frac{1}{1+x+xy+xyz}+\frac{x}{x+xy+xyz+xyzt}+\frac{xy}{xy+xyz+xyzt+xyzt.x}+\frac{xyz}{xyz+xyzt+xyzt.x+xyzt.xy}\)
\(=\frac{1}{1+x+xy+xyz}+\frac{x}{x+xy+xyz+1}+\frac{xy}{xy+xyz+1+x}+\frac{xyz}{xyz+1+x+xy}\)
\(=\frac{1+x+xy+xyz}{1+x+xy+xyz}\)
\(=1\)
Bài 1 :
\(n_{Na2O}=\dfrac{3,1}{62}=0,05\left(mol\right)\)
Pt : \(Na_2O+H_2O\rightarrow2NaOH|\)
1 1 2
0,05 0,05 0,1
\(n_{NaOH}=\dfrac{0,05.2}{1}=0,1\left(mol\right)\)
⇒ \(m_{NaOH}=0,1.40=4\left(g\right)\)
\(C_{NaOH}=\dfrac{4.100}{20}=20\)0/0
Chúc bạn học tốt
(1) \(2KMNO_4\underrightarrow{t^o}K_2MNO_4+MNO_2+O_2\)
(2) \(2Cu+O_2\underrightarrow{t^o}2CuO\)
(3) \(CuO+H_2\underrightarrow{t^o}Cu+H_2O\)
(4) \(2H_2+O_2\underrightarrow{t^o}2H_2O\)
(5) \(Na_2O+H_2O\rightarrow2NaOH\)
(6) \(P_2O_5+3H_2O\rightarrow2H_3PO_4\)
Chúc bạn học tốt