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1) 9 x 10 + 10 x 11 + 11 x 12 + ....+ 2015 x 2016
=9x10x11-8x9x10+10x11x12-9x10x11+...+2015x2016x2017-2014x2015x2013
=2015x2016x2017-8x9x10
=8193537360
99 x 2015 + 2016 = 99 x 2015 + 2015 + 1
= 99 x 2015 + 2015 x 1 + 1
= ( 99 + 1 ) x 2015 + 1
= 100 x 2015 + 1
= 201500 + 1
= 201501
ta co:99x2015+2016=99x2015+2015+1=2015x100+1=201500+1=201501
Ta có: 2015x2016-1=(2014+1)x2016-1=2014x2016+2016-1=2014x2016+2015
A=\(\frac{2015x2016-1}{2014x2016+2015}=\frac{2014x2016+2015}{2014x2016+2015}=1\)\(\)
Vậy A=1
Mọi người tk cho mình nha.Mình cảm ơn nhiều ^-^
\(\frac{2014.2015+2016}{2015.2016-2014}=\frac{2014.2015+2016}{2015.2014+4030-2014}=\frac{2014.2015+2016}{2014.2015+2016}=1\)
\(2015.2017-\frac{1}{2014}+2015.2016\)
\(=2015.\left(2017+2016\right)-\frac{1}{2014}\)
\(=2015.4033-\frac{1}{2014}\)
\(=8126495\)
2014 x 2016 + \(\frac{2017}{2015}\)x 2015 + 2016
= 2014 x 2016 + 2017 + 2016 x 1
= 2016 x ( 2014 + 1 ) + 2017
= 2016 x 2015 + 2017
= 4064257
\(\frac{2015+2014\cdot2016}{2015\cdot2016-1}\)
\(=\frac{2015+\left(2015-1\right)2016}{2015\cdot2016-1}\)
\(=\frac{2015-2016+2015\cdot2016}{2015\cdot2016-1}\)
\(=\frac{2015\cdot2016-1}{2015\cdot2016-1}\)
\(=1\)
SAI ĐỀ RỒI BẠN ƠI
đề đúng là
1 + 2 - 3 - 4 + 5 + 6 - 7 - 8 + 9 + ....... - 2015 - 2016 + 2017
=(2+4+6+8+.......+2016)-(1+3+5+7+.......+2015+2017)=tự tính nhé
\(\frac{2016\cdot2015-1}{2014\cdot2015+4029}\)
\(=\frac{2014\cdot2015+2015\cdot2-1}{2014\cdot2015+4029}\)
\(=\frac{2014\cdot2015+4030-1}{2014\cdot2015+4029}\)
\(=\frac{2014\cdot2015+4029}{2014\cdot2015+4029}=1\)
\(\dfrac{\left(24-6:0,25\right)x2015}{2015x2016}=\dfrac{\left(24-6x4\right)x2015}{2015x2016}=\dfrac{0x2015}{2015x2016}=\dfrac{0x1}{1x2016}=0\)
#\(Sky\)
\(\dfrac{\left(24-6:0,25\right)x2015}{2015x2016}\)
= \(\dfrac{\left(24-24\right)x2015}{2015x2016}\)
= \(\dfrac{0x2015}{2015x2016}\)
= \(\dfrac{0}{2016}=0\)