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\(\frac{12}{15}\times\frac{22}{47}+\frac{25}{47}:\frac{15}{12}\)
\(\frac{12}{15}\times\frac{22}{47}+\frac{25}{47}\times\frac{12}{15}\)
\(=\frac{12}{15}\times\left(\frac{22}{47}+\frac{25}{47}\right)\)
\(=\frac{12}{15}\times\frac{22+25}{47}\)
\(=\frac{12}{15}\times1=\frac{12}{15}\)
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
20162016 x 2017 - 20172017 x 2016 = 2016 x 10001 x 2017 - 2017 x 10001 x 2016
= 0
a ) \(\frac{2016\cdot12+2003+2000\cdot2015+2015}{2015+2015\cdot502+504\cdot2015}\)
\(=\frac{\left(2015+1\right)\cdot12+2003+2000\cdot2015+2015}{2015\cdot\left(1+502+504\right)}\)
\(=\frac{2015\cdot12+12\cdot1+2003+2000\cdot2015+2015}{2015\cdot1007}\)
\(=\frac{2015\cdot12+\left(12\cdot1+2003\right)+2000\cdot2015+2015}{2015\cdot1007}\)
\(=\frac{2015\cdot12+2015+2000\cdot2015+2015}{2015\cdot1007}\)
\(=\frac{2015\cdot\left(12+1+2000+1\right)}{2015\cdot1007}\)
\(=\frac{2015\cdot2014}{2015\cdot1007}\)
\(=2\)
b ) \(\frac{1978\cdot1979+1980\cdot21+1958}{1980\cdot1979-1978\cdot1979}\)
\(=\frac{1978\cdot1979+\left(1979+1\right)\cdot21+1958}{\left(1980-1978\right)\cdot1979}\)
\(=\frac{1979\cdot1978+1979\cdot21+21\cdot1+1958}{2\cdot1979}\)
\(=\frac{1978\cdot1979+1979\cdot21+1979}{2\cdot1979}\)
\(=\frac{\left(1978+21+1\right)\cdot1979}{2\cdot1979}\)
\(=\frac{2000\cdot1979}{2\cdot1979}\)
\(=1000\)
1) 9 x 10 + 10 x 11 + 11 x 12 + ....+ 2015 x 2016
=9x10x11-8x9x10+10x11x12-9x10x11+...+2015x2016x2017-2014x2015x2013
=2015x2016x2017-8x9x10
=8193537360
2016 x 2016-2000 x 2032
=2016 x (2000+16)-2000 x (2016+16)
=2016 x 2000+2016 x 16-2000 x 2016-2000 x 16
=2016 x 16-2000 x 16
=(2016-2000) x 16
=16 x 16
=256
2016 x 2016 - 2000 x 2032
= 2016 x 2016 - 2000 x ( 2016 + 16 )
= 2016 x 2016 - 2000 x 2016 - 2000 x 16
= 2016 x ( 2016 - 2000 ) - 2000 x 16
= 2016 x 16 - 2000 x 16
= 16 x ( 2016 - 2000 )
= 16 x 16
= 256
Cấm ai chép nhé
= 64000 + 256
= 64256