tính bằng cách thuận tiện nếu có thể: ( 2013 x 2014 + 2014 x 2015 + 2015 x 2016) x ( 1 + 1/3 - 4/3)
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( 2014 x 2015 - 2016 ) : ( 2012 + 2013 x 2014 )
= ( 4058210 - 2016 ) : ( 2012 + 4054182 )
= 4056194 : 4056194
= 1
a) 20,8 x 45 + 0,37 x 15 + 20,8 x 55 x 0,63
= 20,8 x ( 45 + 55 x 0,63 ) + 0,37 x 15
= 20,8 x ( 45 + 34,65 ) + 5,55
= 20,8 x 79,65 + 5,55
= 1656,72 + 5,55
= 1662,27
b) ( 2013 x 2014 + 2014 x 2015 + 2015 x 2016 ) x ( 1 + 1/3 - 1 và 1/3 )
= ( 2013 x 2014 + 2014 x 2015 + 2015 x 2016 ) x [( 1 - 1 ) + ( 1/3 - 1/3 ) ]
= ( 2013 x 2014 + 2014 x 2015 + 2015 x 2016 ) x 0
= 0
( 2013 x 2014 +2014 x 2015 + 2015 x 2016 ) x ( 1 + 1/3 - 1 - 1/3 )
= ( 2013 x 2014 + 2014 x 2015 + 2015 x 2016 ) x 0
= 0
\(\dfrac{x-1}{2012}+\dfrac{x-2}{2013}+\dfrac{x-3}{2014}=\dfrac{x-4}{2015}+\dfrac{x-5}{2016}+\dfrac{x-6}{2017}\)
\(\Leftrightarrow\left(\dfrac{x-1}{2012}+1\right)+\left(\dfrac{x-2}{2013}+1\right)+\left(\dfrac{x-3}{2014}+1\right)=\left(\dfrac{x-4}{2015}+1\right)+\left(\dfrac{x-5}{2016}+1\right)+\left(\dfrac{x-6}{2017}+1\right)\)
\(\Leftrightarrow\dfrac{x+2011}{2012}+\dfrac{x+2011}{2013}+\dfrac{x+2011}{2014}-\dfrac{x+2011}{2015}-\dfrac{x+2011}{2016}-\dfrac{x+2011}{2017}=0\)
\(\Leftrightarrow\left(x+2011\right)\left(\dfrac{1}{2012}+\dfrac{1}{2013}+\dfrac{1}{2014}-\dfrac{1}{2015}-\dfrac{1}{2016}-\dfrac{1}{2017}\right)=0\)
\(\Leftrightarrow x=-2011\)( do \(\dfrac{1}{2012}+\dfrac{1}{2013}+\dfrac{1}{2014}-\dfrac{1}{2015}-\dfrac{1}{2016}-\dfrac{1}{2017}\ne0\))
Ta có P(x)= x4+ax3+bx2+cx+d
Đặt P(x)= (x-2013)(x-2014)(x-2015)(x-x0)+mx2+nx+p
P(2013)=2014=>4052169m+2013n+p=2014} m=0
P(2014)=2015=>4056196m+2014n+p=2015}=> n=1
P(2015)=2016=>4060225m+2015n+p=2016} p=1
=>P(x)= (x-2013)(x-2014)(x-2015)(x-x0)+x+1
=>.) P(2012)= -6(2012-x0)+2012+1
= -12072+6x0+2013=-10059+6x0
.)P(2016)=6(2016-x0)+2016+1
=12096-6x0+2017=14113-6x0
=> P(2012)+P(2016)= -10059+6x0+14113-6x0=4054
( 2013 x 2014 + 2014 x 2015 + 2015 x 2016) x ( 1 + 1/3 - 4/3)
=( 2013 x 2014 + 2014 x 2015 + 2015 x 2016) x ( 4/3 - 4/3)
=( 2013 x 2014 + 2014 x 2015 + 2015 x 2016) x 0
=0
Ta có: \(\left(2013\cdot2014+2014\cdot2015+2015\cdot2016\right)\left(1+\dfrac{1}{3}-\dfrac{4}{3}\right)\)
\(=\left(2013\cdot2014+2014\cdot2015+2015\cdot2016\right)\left(\dfrac{3}{3}+\dfrac{1}{3}-\dfrac{4}{3}\right)\)
=0