bài 1 timd x để p/s sau nhận giá trị âm

1, \(\frac{14-1}{x^2+8}\)2,\(\frac{-37-x^2}{41+x}\)3, \(\frac{x+2}{x-7}\)

bài 2 tìm x để p/s sau nhận giá trị dương

1, \(\frac{\left(x+1\right)^2}{x+3}\)2, \(\frac{x+19}{x+20}\)

bài 3 tìm x để biểu htucws sau là 1 phân số

1, \(\frac{3x}{x^2+2}\)2, \(\frac{5+x}{x\left(x-11\right)}\)3, \(\frac{x}{x+30}\)

Bài 1

\(\frac{1}{2}+\frac{1}{2.3}+\frac{1}{3.4}+.......+\frac{1}{x.\left(x+1\right)}=\frac{49}{50}\)

\(\frac{2x+3}{x-1}\)có giá trị là số nguyên \(\left(x\inℤ,x\ne0\right)\)

\(\frac{x-4}{y-3}=\frac{4}{3}\)và \(x-y=5\)\(\left(y\ne3\right)\)

Tìm x,y nguyên dương để: \(\frac{1}{x}+\frac{y}{2}=\frac{5}{8}\)

\(\left(x+3\right)^2+\left(y-1\right)^2< 4\left(x;y\inℤ\right)\)

\(\left(x+3\right)^2.\left(y-3\right)=-4\left(x;y\inℤ\right)\)

Bài 1:tính giá trị biểu thức sau:

\(B=\left(1-\frac{1}{21}\right).\left(1-\frac{1}{28}\right).\left(1-\frac{1}{36}\right)...\left(1-\frac{1}{1326}\right)\) 

Bài 2 tìm x biết

\(a,1\frac{1}{30}:\left(24\frac{1}{6}-24\frac{1}{5}\right)-\frac{1\frac{1}{2}-\frac{3}{4}}{4x-\frac{1}{2}}=\left(-1\frac{1}{15}\right):\left(8\frac{1}{5}-8\frac{1}{3}\right)\)

\(b,\left|3x-\frac{2}{5}\right|=\frac{1}{35}+\left|\frac{-3}{7}\right|\)

\(c,-3\frac{1}{2}-\left(2x+\frac{1}{2}\right):\left(-\frac{3}{7}\right)=0\)

\(d,\left(x-4\right).\left(x+2\right)\le0\)với x thuộc z

giúp mk với

1.Cho A =\(\frac{5n-11}{n-2}\left(n\inℤ\right)\)

a. Tìm điều kiện n để A là phân số 

b.Tìm n \(\inℤ\)để A có giá trị nguyên 

c.Tìm giá trị lớn nhất của A

2.Tìm x

a. \(\frac{3}{4}\times\left(\frac{1}{2}x+\frac{1}{3}\right)-\frac{1}{2}=\frac{2}{3}x-\frac{1}{4}\)

b.\(\frac{2}{3}x-3x+\frac{1}{5}=\frac{3}{2}\left(x-\frac{1}{4}\right)-\frac{3}{2}\)

3.a.Chứng tỏ :

\(\frac{1}{7^2}+\frac{1}{8^2}+..................+\frac{1}{99^2}< \frac{1}{6}\)

b.Chứng tỏ:

\(\frac{1}{3}+\frac{1}{4}+\frac{1}{5}+\frac{1}{6}+\frac{1}{7}+\frac{1}{8}+\frac{1}{9}+\frac{1}{10}+\frac{1}{11}+\frac{1}{12}+............+\frac{1}{23}< 3\)

bài 2 tìm x

a,\(\frac{-2}{3}.x+\frac{1}{5}=\frac{3}{10}\)

b,\(\left|x\right|-\frac{3}{4}=\frac{5}{3}\)

c,\(\frac{2}{3}.x-\frac{1}{2}=\frac{1}{10}\)

d,\(\frac{3}{5}+\frac{4}{9}:x=\frac{2}{3}\)

e,\(\left|x+75\%\right|=2\frac{1}{5}\)

i,\(\left(x+\frac{1}{2}\right).\left(\frac{2}{3}-2.x\right)=0\)

k,\(\frac{4}{7}.x-\frac{2}{3}=\frac{1}{5}\)

l,\(\frac{2}{3}.x-\frac{3}{2}.x=\frac{5}{12}\)

m,\(\left|2.x-\frac{1}{3}\right|+\frac{5}{6}=1\)

n,\(\frac{1}{3}-\frac{7}{8}.x=\frac{1}{3}\)

11,\(\frac{x+2}{5}=\frac{7}{12}-1\frac{1}{4}\)

12,\(\left(2\frac{4}{5}.x-50\right):\frac{2}{3}=51\)

13,\(\frac{2}{5}+\frac{3}{5}.\left(3.x-3,7\right)=-\frac{53}{10}\)

14,\(\frac{7}{9}:\left(2+\frac{3}{4}.x\right)+\frac{5}{9}=\frac{23}{27}\)

1. tinh` giá trị biểu thức ( tính nhanh nếu có thế )

\(a)\frac{-6}{11}.\frac{5}{13}+\frac{-6}{11}.\frac{8}{13}-\left(\frac{-2}{5}\right)^0\) \(b)\left(2\frac{2}{3}+3\frac{1}{2}\right);\left(4\frac{3}{4}-2\frac{1}{6}\right)+\frac{19}{31}\) \(c)2,4:\left(-2\right)^3+\left(3-\frac{9}{11}\right).1\frac{3}{8}\)

\(d)\left(-\frac{3}{4}\right)^2:\frac{-3}{8}+\frac{1}{2}-\frac{3}{4}-\left(\frac{-78}{57}\right)^0\)

2. tìm x

\(a)x+\frac{-1}{5}=\left(-\frac{3}{4^{ }}\right)^2\) \(b)\left|\frac{5}{2}x+\frac{2}{3}\right|-\frac{1}{4}=0\) \(c)\frac{2}{3}x-\frac{1}{2}=\frac{5}{12}+\frac{1}{2}x\) \(d)\left(x-\frac{1}{4}\right)^4=\frac{1}{81}\)

\(e)4x+3\frac{1}{4}=x-\frac{1}{4}\) \(g)\left(x-\frac{1}{3}\right)^3=\frac{1}{27}\)

tìm x

a) \(\frac{x-1}{2}+\frac{x-2}{5}=\frac{1}{4}+\frac{x-7}{10}\)

b) \(3-\frac{2}{2x-3}=\frac{2}{5}+\frac{1}{2x-3}-\frac{3}{2}\)

c)\(7\cdot\left(x-1\right)+2x\cdot\left(1-x\right)=0\)

d) \(\frac{x+1}{2008}+\frac{x+2}{2017}+\frac{x+3}{2016}=\frac{x+10}{2009}+\frac{x+11}{2008}+\frac{x+12}{2007}\)

e) \(\frac{2}{\left(x-1\right)\cdot\left(x-3\right)}+\frac{5}{\left(x-3\right)\cdot\left(x-8\right)}+\frac{12}{\left(x-8\right)\cdot\left(x-20\right)}-\frac{1}{x-20}=\frac{-3}{4}\)