Tính nhanh :
(5+10+15+....+1000)+\(\left(\frac{2}{5}:0,5+2.\left(-0,4\right)\right):\left(\frac{1}{5}+\frac{1}{10}+....+\frac{1}{2012}\right)\)
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tính
B= (5+10+15+....+1000)\(\left[\frac{2}{5}:0,5+2.\le\left(-0,4\right)\right]\)
C=\(\left(\frac{1}{5}+\frac{1}{10}+\frac{1}{15}+....+\frac{1}{1000}\right)\)
Sao trong biểu thức B lại có dấu " </"?
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a)\(\frac{-5}{9}.\left(\frac{3}{10}-\frac{2}{5}\right) \)
b)\(\frac{1}{2}\sqrt[]{64-\sqrt{\frac{4}{25}+1^{2012}}}\)
c) \(9.\left(\frac{1}{3}\right)^3:\left[\left(\frac{-2}{3}\right)^2+0,5-1\frac{1}{2}\right]\)
d)\(\frac{-5}{9}.\left(\frac{3}{10}-\frac{2}{5}\right)\)
Tính nhanh
a)\(\frac{120-\left(-0,5\right).\left(-40\right).\left(-5\right).\left(-0,2\right).20.0,25}{5+10+15+...+1995}\)
b)\(\frac{5.18-10.27+15.36}{10.36-20.54+30.72}\)
c)\(\left(\frac{1}{2}-1\right)\left(\frac{1}{3}-1\right)\left(\frac{1}{4}-1\right)...\left(\frac{1}{1999}-1\right)\)
\(\frac{5.18-10.27+15.36}{10.36-20.54+30.72}\)
\(=\frac{5.18-10.27+15.36}{5.2.18.2-10.2.27.2+15.2.36.2}\)
\(=\frac{5.18-10.27+15.36}{5.8.2.2-10.27.2.2+15.36.2.2}\)
\(=\frac{1}{2.2-2.2+2.2}\)
\(=\frac{1}{2.2}=\frac{1}{4}\)
Giúp mik với
trước 5h nha
a) \(\frac{120-\left(-0,5\right).\left(-40\right).\left(-5\right).\left(-0,2\right).20.0,25}{5+10+15+...+1995}\)
\(=\frac{120-\left[\left(-0,5\right).\left(-0,2\right)\right].\left[\left(-40\right).0,25\right].\left[\left(-5\right).\left(20\right)\right]}{\left(1995+5\right).\left[\left(1995-5\right)\div5+1\right]\div2}\)
\(=\frac{120-0,1.\left(-10\right).\left(-100\right)}{2000.399\div2}\)
\(=\frac{120-100}{1000.399}\)
\(=\frac{1}{19950}\)
b) \(\frac{5.18-10.27+15.36}{10.36-20.54+30.72}\)
\(=\frac{5.18-2.5.27+3.5.36}{10.2.18-20.2.27+5.2.3.2.36}\)
\(=\frac{5.18-2.5.27+3.5.36}{20.18-20.2.27+20.3.36}\)
\(=\frac{5.\left(18-2.27+3.36\right)}{20.\left(18-2.27+3.36\right)}\)
\(=\frac{1}{4}\)
c) \(\left(\frac{1}{2}-1\right)\left(\frac{1}{3}-1\right)\left(\frac{1}{4}-1\right)...\left(\frac{1}{1999}-1\right)\)
\(=\left(\frac{-1}{2}\right).\left(\frac{-2}{3}\right).\left(\frac{-3}{4}\right)...\left(\frac{-1998}{1999}\right)\)
\(=\frac{\left(-1\right).\left(-2\right).\left(-3\right)...\left(-1998\right)}{2.3.4...1999}\)
\(=\frac{\left(-1\right).\left(-1\right).\left(-1\right)...\left(-1\right)}{1.1.1...1999}\)
Ta có : 1998 số (-1) mà 1998 là số chẵn
Vậy tích của 1998 số (-1) = 1
\(\Rightarrow\frac{\left(-1\right).\left(-1\right).\left(-1\right)...\left(-1\right)}{1.1.1...1999}\)
\(=\frac{1}{1999}\)
Tính Nhanh:\(\frac{\left(\frac{1}{10}-\frac{\sqrt{2}}{7}+\frac{3\sqrt{2}}{35}\right).\left(-\frac{4}{15}\right)}{\left(\frac{1}{10}+\frac{3\sqrt{2}}{25}-\frac{\sqrt{2}}{5}\right).\frac{5}{7}}\)
Tính:
a)\(\left\{\left[\left(6,2:0,31-\frac{5}{6}.0,9\right).0,2+0,15\right]:0,2\right\}:\left[\left(2+1\frac{4}{11}:0,1\right).\frac{1}{33}\right]\)
b)\(0,4\left(3\right)+0,6\left(2\right)-2\frac{1}{2}.\left[\left(\frac{1}{2}+\frac{1}{3}:0,5\left(8\right)\right)\right]:\frac{50}{53}\)
c)\(\frac{0,375-0,3+\frac{3}{11}+\frac{3}{12}}{0,625-0,5+\frac{5}{11}+\frac{5}{12}}\)
c) \(\frac{0,375-0,3+\frac{3}{11}+\frac{3}{12}}{0,625-0,5+\frac{5}{11}+\frac{5}{12}}=\frac{3\left(0,125-0,1+\frac{1}{11}+\frac{1}{12}\right)}{5\left(0,123-0,1+\frac{1}{11}+\frac{1}{12}\right)}=\frac{3}{5}\)
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Tính nhanh:
\(\frac{\left(\frac{1}{14}-\frac{\sqrt{2}}{7}+\frac{3\sqrt{2}}{25}\right).\left(-\frac{4}{15}\right)}{\:\left(\frac{1}{10}+\frac{3\sqrt{2}}{25}-\frac{\sqrt{2}}{5}\right).\left(\frac{5}{7}\right)}\)
Tinh nhanha) frac{120-left(-0,5right).left(-40right).left(-5right).left(-0,2right).20.0,25}{5+10+15+...+1995}b)frac{5.18-10.27+15.36}{10.36-20.54+30.72}c)left(frac{1}{2}-1right)left(frac{1}{3}-1right)left(frac{1}{4}-1right)...left(frac{1}{1999}-1right)d)-1frac{1}{2}.left(-1frac{1}{3}right).left(-1frac{1}{4}right)...left(-1frac{1}{1999}right)
Đọc tiếp
Tinh nhanh
a) \(\frac{120-\left(-0,5\right).\left(-40\right).\left(-5\right).\left(-0,2\right).20.0,25}{5+10+15+...+1995}\)
b)\(\frac{5.18-10.27+15.36}{10.36-20.54+30.72}\)
c)\(\left(\frac{1}{2}-1\right)\left(\frac{1}{3}-1\right)\left(\frac{1}{4}-1\right)...\left(\frac{1}{1999}-1\right)\)
d)\(-1\frac{1}{2}.\left(-1\frac{1}{3}\right).\left(-1\frac{1}{4}\right)...\left(-1\frac{1}{1999}\right)\)
Thực hiện phép tính:
a) \(\left(\frac{1}{3}-1\right).\left(\frac{1}{6}-1\right).\left(\frac{1}{10}-1\right).\left(\frac{1}{15}-1\right)...\left(\frac{1}{1225}-1\right).\left(\frac{1}{1275}-1\right)\)
b) 1 - 2 + 3 - 4 + 5 - 6 + ... + 2011 - 2012
B
từ 1 đến 2012 có tất cả:
2012-1:1+1 = 2012 (số)
=>có: 2012:2 = 1006 (cặp)
Mà mỗi cặp bằng (-1)nên
tổng dãy số trên là: 1006 . (-1) = -1006
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(1-2)+(2-3)+(3-4)+(5-6)+...+(2011-2012)
=-1+(-1)+(-1)+(-1)+...+(-1)
có tất cả các số -1 trên dãy số trên là
(2012-2);2+1=1006
vậy suy ra ; -1x1006=(-1006)
chac chan la dung
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\(\left[3,5+10\times\left(0,4\right)^2\right]\div\left[\left(0,5\right)^2-\left(\frac{1}{5}\right)^3+2,758\right]\)
\(\left[3,5+10.\left(0,4\right)^2\right]:\left[\left(0,5\right)^2-\left(\frac{1}{5}\right)^3+2,758\right]\)
\(=\left(3,5+1,6\right):\left[\frac{1}{4}-\frac{1}{125}+2,758\right]\)
\(=5,1:\left[\frac{125}{500}-\frac{4}{500}+\frac{1379}{500}\right]\)
\(=5,1:3\)
\(=1,7\)
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