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x - ( 3,3 + 2,4 ) = 11,6
x - 5,7 =11,6
x = 11,6 + 5,7
x = 17,3
<=>x-5,7=11,6 <=>x-4,6=1,8+2,6
<=>x =11,6+5,7=17,3 <=>x-4,6=4,4
Vậy x=17,3 <=>x =4,4+4,6=9 Vậy x=9
<=>x+1,8=15,02+0,91=15,93 <=>5.x=47-27=20
<=>x =15,93-1,8=14,13 <=>x =20:5=4
Vậy x=14,13 Vậy x=4
<=>x:3=0,312 8.x-3.x=1,95
<=>x =0,312.3 x.5 =1,95
<=>x =0,931 x =1,95:5
Vậy x=0,936 x=0,19 vậy x=0,19
<=>x:2=2,43+8,6=11,03
<=>x =11,03.2= 22,06
Vậy x=22,06
1) \(16,2\times3,7+5,7\times16,2-7,8\times4,8-4,6\times7,8\)
\(=16,2.\left(3,7\times5,7\right)-7,8.\left(4,8\times4,6\right)\)
\(=16,2.9,4-7,8.9,4\)
\(=9,4.\left(16,2-7,8\right)\)
\(=9,4.8,4=78,96\)
2) \(11,2+12,3+13,4-12,6-11,5-10,4\)
\(=\left(11,2-10,4\right)+\left(12,3-11,5\right)+\left(13,4-12,6\right)\)
\(=0,8+0,8+0,8\)
\(=0,8.3=2,4\)
1) 16,2×3,7+5,7×16,2−7,8×4,8−4,6×7,816,2×3,7+5,7×16,2−7,8×4,8−4,6×7,8
=16,2.(3,7×5,7)−7,8.(4,8×4,6)=16,2.(3,7×5,7)−7,8.(4,8×4,6)
=16,2.9,4−7,8.9,4=16,2.9,4−7,8.9,4
=9,4.(16,2−7,8)=9,4.(16,2−7,8)
=9,4.8,4=78,96=9,4.8,4=78,96
2) 11,2+12,3+13,4−12,6−11,5−10,411,2+12,3+13,4−12,6−11,5−10,4
=(11,2−10,4)+(12,3−11,5)+(13,4−12,6)=(11,2−10,4)+(12,3−11,5)+(13,4−12,6)
=0,8+0,8+0,8=0,8+0,8+0,8
=0,8.3=2,4
a,2xX-7/4=11/6
=> 2x = 11/6 + 7/4
=> 2x = 43/12
=> x = 43/24
a/
$A-3=\frac{2003}{2004}+\frac{2004}{2005}+\frac{2005}{2003}-3$
$=(1-\frac{1}{2004})+(1-\frac{1}{2005})+(1+\frac{2}{2003})-3$
$=\frac{2}{2003}-\frac{1}{2004}-\frac{1}{2005}$
$=(\frac{1}{2003}-\frac{1}{2004})+(\frac{1}{2003}-\frac{1}{2005})$
$>0+0=0$
$\Rightarrow A>3$
b/
$B=\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+....+\frac{1}{2015^2}$
$< \frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{2014.2015}$
$=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{2014}-\frac{1}{2015}$
$=1-\frac{1}{2015}<1$
\(C=-1-1-1-...-1\)
C có \(\left(2016-1+1\right):2=1008\left(\text{số hạng -1}\right)\)
\(\Rightarrow C=\left(-1\right)\cdot1008=-1008\)
\(D=\left(1+2+...+15\right)-\left(6+7+...+20\right)\\ D=\dfrac{\left(15+1\right)\left(15+1-1\right)}{2}-\dfrac{\left(20+6\right)\left(20-6+1\right)}{2}\\ D=\dfrac{16\cdot15-26\cdot15}{2}=-75\)
b) 45,3 : 2,6 - 19,3 : 2,6
= (45,3-19,6) : 2,6
= 26 : 2,6
= 10
d) 1+2+3+...+100
Ta có : 1 = 1 x 2 ; 2 = 1 x 2 ; 3 = 1 x 3 ; ..... ; Vậy 100 = 1 x 100
1+2+3+....+100 = (1+100).100:2 = 5050