Tính nhanh:
2012*2013+2014
2014*2013+2
1.so sánh các phân số sau bằng cách nhanh nhất
a)\(\frac{2012}{2013}và\frac{2013}{2014}\) b)\(\frac{1006}{1007}và\frac{2013}{2015}\) c)\(\frac{64}{73}và\frac{45}{51}\) d)\(\frac{2323}{2424}và\frac{20132013}{20142014}\)
a) Ta có: \(\frac{2012}{2013}+\frac{1}{2013}=1\)
\(\frac{2013}{2014}+\frac{1}{2014}=1\)
Vì \(\frac{1}{2013}>\frac{1}{2014}\) nên \(\frac{2012}{2013}< \frac{2013}{2014}\)
Vậy: \(\frac{2012}{2013}< \frac{2013}{2014}\)
b) \(\frac{1006}{1007}+\frac{1}{1007}=1\)
\(\frac{2013}{2015}+\frac{2}{2015}=1\)
Mà \(\frac{1}{1007}=\frac{2}{2014}>\frac{2}{2015}\)
nên: \(\frac{1006}{1007}< \frac{2013}{2015}\)
Vậy:.......
Tính nhanh : 2011 x 2012 + 2013 x 21 + 1991 / 2012 x 2013 - 2012 x 2012
\(\frac{2011\times2012+2013\times21+1991}{2012\times2013-2012\times2012}\)
\(=\frac{2011\times2012+2013\times\left(21+1991\right)}{2012\times2013-2012\times2012}\)
\(=\frac{2011\times2012+2013\times2012}{2012\times2013-2012\times2012}=\frac{2011}{2012}\)
TÍNH NHANH ;
A= 1*2+2*3+3*4+....+2011*2012
B =2012*2013+2013*2014
Cho M = 2014 . 2015 - 2 / 2013 + 2013 . 2015
N= -2014 . 20152015 / 20142014 . 2015
Tính M + N
Tính nhanh
2013 x 2012 - 1/2011 x 2013 + 2012
tính nhanh:
2012*2013+2014
2014*2013+2
Tính nhanh:
2012 x 1001 - 2012 + 2013 x 999 + 2013
= 2012 x (1001-1) + 2013 x (999+1)
= 2012 x 1000 + 2013 x 1000
= 1000 x (2012+2013)
= 1000 x 4025 = 4025000
k mk nha
= 2012 x (1001-1) + 2013 x (999+1)
= 2012 x 1000 + 2013 x 1000
= 1000 x (2012+2013)
= 1000 x 4025 = 4025000
2012 x (1001-1)+2013 x (999+1)
=2012 x 1000 + 2013 x 1000
=1000 x (2012 + 2013)
=1000 x 4025=4025000
k cho chị nha cưng!
Tính nhanh :
a) 2012 x 2013 - 1013 x 2013 + 2013 =
2012 x 2013 - 1013 x 2013 + 2013
= 2012 x 2013 - 1013 x 2013 + 2013 x 1
= 2013 x ( 2012 - 1013 + 1 )
= 2013 x 1000
= 2013000
a) 2012x2013-1013x2013+2013
=2013(2012-1013+1)
=2013x1000
=2013000
\(2012x2013-1013x2013+2013\)
\(=2013x\left(2012-1013+1\right)\)
\(=2013x1000\)
\(=2013000\)
Nhớ ấn đúng cho mình nha!
Tính nhanh B = \(2013+\frac{2013}{1+2}+\frac{2013}{1+2+3}+\frac{2013}{1+2+3+4}+...+\frac{2013}{1+2+3+4+...+2012}\)
=> B=2013. (1+\(\frac{1}{1+2}\) +\(\frac{1}{1+2+3}\) +...+ \(\frac{1}{1+2+3+...+2012}\))
=>B= 2013.(\(\frac{2}{2}\) + \(\frac{2}{2.3}\) +\(\frac{2}{3.4}\) +...+\(\frac{2}{2012.2013}\))
=>B= 2013.2.(\(\frac{1}{1.2}\) + \(\frac{1}{2.3}\) +\(\frac{1}{3.4}\) +...+\(\frac{1}{2012.2013}\))
=>B=4026. (1-\(\frac{1}{2}\) +\(\frac{1}{2}\) -\(\frac{1}{3}\) + ...+\(\frac{1}{2012}\) - \(\frac{1}{2013}\))
=>B=4026.(1-\(\frac{1}{2013}\))
=>B=4026.\(\frac{2012}{2013}\) => B=2.2012=4024 Vậy B=4024