\(\frac{3}{2^2}.\frac{8}{3^2}.\frac{15}{4^2}.........\frac{899}{30^2}\)
A= \(\frac{1.3.2.4.3.5...29.31}{2.2.3.3...30.30}\)
A=\(\frac{\left(2.3...29.30\right)\left(3.4.5...29.31\right)}{\left(2.3.4...30\right)\left(2.3.4...30\right)}\)
A=\(\frac{31}{2.30}\)
A=\(\frac{31}{60}\)
Bài 1:
\(\frac{32}{15}:\left(-1\frac{1}{5}+1\frac{1}{3}\right)\) \(1\frac{13}{15}.0,75-\left(\frac{8}{15}+0.25\right).\frac{24}{47}\)
\(0,2.\frac{15}{36}-\left(\frac{2}{5}+\frac{2}{3}\right):1\frac{1}{5}\) \(5:\left(4\frac{25}{28}-1\frac{25}{28}\right)-1\frac{3}{8}:\left(\frac{3}{8}+\frac{9}{20}\right)\)
1. thực hiện phép tính
B= \(5\frac{3}{5}.\left(0,5\right)^2+\left(\frac{8}{5}-25\%\right):4\frac{1}{4}\)
2.tính nhanh
a.\(2\frac{1}{9}.14\frac{2}{5}-2\frac{1}{9}.5\frac{2}{5}\) b) -1,7 .2,3.+1,7+(-3,7)-1,7 .3-0,17:0,1
3. tìm x
a) x-30% x=\(\frac{1}{2}\) b)\(\left(3\frac{1}{2}+2x\right):1\frac{5}{7}=2\frac{1}{3}\)
Bài 5 : Chững minh rẳng :
a) S= \(\frac{3}{10}+\frac{3}{11}+\frac{3}{12}+\frac{3}{13}+\frac{3}{14}\) CMR :1< S <2
b) \(\frac{1}{4^2}+\frac{1}{6^2}+\frac{1}{8^2}+\frac{1}{10^2}+...+\frac{1}{\left(2n\right)^2}< \frac{1}{4}\)
c) \(\frac{3}{4}+\frac{8}{9}+\frac{15}{16}+...+\frac{2499}{2500}>48\)
d) \(\frac{1}{5}+\frac{1}{13}+\frac{1}{14}+\frac{1}{15}+\frac{1}{61}+\frac{1}{62}+\frac{1}{63}< \frac{1}{2}\)
Bài :So sánh phân số sau:
a)\(\frac{1985.1987-1}{1980+1985.1986}và1\)
b) A= \(\frac{13^{15}+1}{13^{16}+1}\)và B = \(\frac{13^{16}+1}{13^{17}+1}\)
c)\(\frac{18}{53}và\frac{26}{79}\)
d)\(\frac{5}{8}và\frac{14}{17}\)
e)\(\frac{1}{5^{199}}và\frac{1}{3^{300}}\)
g)\(\frac{1}{3^{17}}và\frac{1}{5^{10}}\)
h) \(\frac{18}{109}và\frac{5}{30}\)
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
\(a)x+\frac{-1}{5}=\left(-\frac{3}{4^{ }}\right)^2\) \(b)\left|\frac{5}{2}x+\frac{2}{3}\right|-\frac{1}{4}=0\) \(c)\frac{2}{3}x-\frac{1}{2}=\frac{5}{12}+\frac{1}{2}x\) \(d)\left(x-\frac{1}{4}\right)^4=\frac{1}{81}\)
\(e)4x+3\frac{1}{4}=x-\frac{1}{4}\) \(g)\left(x-\frac{1}{3}\right)^3=\frac{1}{27}\)
\(a,\frac{2}{3}x-\frac{1}{2}=\frac{1}{10}\) ;\(b,5\frac{4}{7}:x=13\) ;\(c,\left(2\frac{4}{5}x-50\right):\frac{2}{3}=51\)
\(d,\frac{2}{3}+\frac{1}{3}:x=\frac{3}{5}\) ;\(e,8\frac{2}{3}:x-10=-8\)
\(g,x+30\%x=-1,3\) ;\(i,3\frac{1}{3}x+16\frac{3}{4}=-13,25\)
\(k,\left(2\frac{4}{5}x-50\right):\frac{2}{3}=51\) ;m,/2x-1/=\(\left(-4^2\right)\)
1. thực hiện phép tính
a) \(\frac{-1}{2}-\frac{9}{8}:0,75\) b)\(\frac{4}{3}.\frac{11}{15}+\frac{4}{15}.\frac{4}{3}-2\frac{1}{3}\) c)\(\frac{6}{8}+\frac{6}{56}+\frac{6}{140}+.....+\frac{6}{416}\)
2. tìm x
a) x ∈ Z, x∈ Ư (4) và x ∠1 b)x - \(\frac{2}{3}\)=20 % c) \((2\frac{1}{6}-x):\frac{2}{3}=\left(-\frac{1}{2}\right)^2\)
\(a,\frac{3}{4}-x=1\) \(b,x+4=\frac{1}{5}\) \(c,x-\frac{1}{5}=2\)
\(d,x+\frac{5}{3}=\frac{1}{81}\) \(e,x-\frac{10}{3}=\frac{7}{15}.\frac{3}{5}\) \(g,x+\frac{3}{22}=\frac{27}{121}.\frac{11}{9}\)
\(h,1-x=\frac{49}{65}.\frac{5}{7}\) \(i,\frac{8}{23}.\frac{46}{24}-x=\frac{1}{3}\) \(k,\frac{62}{7}.x=\frac{29}{9}:\frac{3}{56}\)
\(g,6\frac{4}{5}-\left(1\frac{2}{3}+3\frac{4}{5}\right)\)
\(h,7\frac{5}{9}-\left(2\frac{3}{4}+3\frac{5}{9}\right)\)
\(i,6\frac{5}{7}-\left(1\frac{3}{4}+2\frac{5}{7}\right)\)
\(k,7\frac{5}{11}-\left(2\frac{3}{7}+3\frac{5}{11}\right)\)
giúp mk với
bài yêu cầu tính nhanh nha
tìm số nguyên x biết :
\(a,\frac{x}{5}=\frac{2}{5}\) \(b,\frac{3}{8}=\frac{6}{x}\) \(c,\frac{1}{9}=\frac{x}{27}\)
\(d,\frac{4}{x}=\frac{8}{6}\) \(c,\frac{3}{x-5}=\frac{-4}{x+2}\) \(g,\frac{x}{-2}+\frac{-8}{x}\)
giúp mk với !!!!!!
