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54x129-54x69+45x59
=54x(128-69)+46x59
=54x59+46x59
=59x(54+46)
=59x100
=5900
nhé
\(A=\left(-2a+3b-4c\right)-\left(-2a-3b-4c\right)\)
\(a,=-2a+3b-4c+2a+3b+4c\)
\(=\left(-2a+2a\right)+\left(3b+3b\right)+\left(-4c+4c\right)\)
\(=0+\left(3b+3b\right)+0\)
\(=3b+3b=2.3b\)
\(b,\)Thay \(a=2012;b=-1;c=-2013\)vào biểu thức \(A\) ta có \(:\)
\(A=\left[-2.2012+3.\left(-1\right)-4.\left(-2013\right)\right]\)\(-\left[-2.\left(2012\right)-3.\left(-1\right)-4.\left(-2013\right)\right]\)
\(A=0\)
A = 47 x 36 + 64 x 47 + 15
A= 47 x ( 64 + 36 ) + 15 = 47 x 100 + 15 = 4700 + 15 = 4715
vậy A= 4715
B= 27+35 + 65 + 73+ 75
B= (27+ 73) + ( 35 + 65) +75
B= 100 +100 +75 = 275
vậy B= 275
C= 37 +37 x 15 +37 x 84
C= 37 x ( 1+15 +84 )= 37 x 100 = 3700
vậy C= 3700
D = 1/20x21 + 1/21x22 + 1/22x23 + 1/23x24
D= 1/20 - 1/21 + 1/21 - 1/22 + 1/22 - 1/23 + 1/23 - 1/24
D= 1/20 -1/24 = 1/120 vậy D= 1/120
E= 1/1x2 + 1/2x3 + ...... + 1/49x50
E= 1/1 - 1/2 + 1/2 - 1/3 +...... + 1/49 - 1/50
E = 1 - 1/50 = 49/50
vậy E= 49/50
CHÚC HOK TOT
(-12)+(-35)+(-8)
=[(-12)+(-8)]+(-35)
=(-20)+(-35)
=-55
(-37)+65+(-12)+(-1)
={(-37)+[(-12)+(-1)]}+65
=[(-37)+(-13)]+65
=-50+65
=15
tick nha
(-12)+(-35)+(-12)
=[(-12)+(-8)]+(-35)
=(-20)+(-35)
=-55
(-37)+65+(-12)+(-1)
=[(-37)+(-12)+(-1)]+65
=-50+65
=15
\(A=47.36+64.47+15\)
\(A=47.\left(36+64\right)+15\)
\(A=47.100+15\)
\(A=4700+15\)
\(A=4715\)
\(B=27+35+65+73+75\)
\(B=\left(27+73\right)+\left(35+65\right)+75\)
\(B=100+100+75\)
\(B=275\)
\(C=37+37.15+84.37\)
\(C=37.\left(1+15+84\right)\)
\(C=37.100\)
\(C=3700\)
\(D=\frac{1}{20.21}+\frac{1}{21.22}+\frac{1}{22.23}+\frac{1}{23.24}\)
\(D=\frac{1}{20}-\frac{1}{21}+\frac{1}{21}-\frac{1}{22}+\frac{1}{22}-\frac{1}{23}+\frac{1}{23}-\frac{1}{24}\)
\(D=\frac{1}{20}-\frac{1}{24}\)
\(D=\frac{24}{480}-\frac{20}{480}\)
\(D=\frac{4}{480}=\frac{1}{120}\)
\(E=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{49.50}\)
\(E=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\)
\(E=1-\frac{1}{50}\)
\(E=\frac{49}{50}\)
(x+1/2).(2/3-2x)=0
suy ra x+1/2=0
x =0-1/2=-1/2
2/3-2x=0
2x=0+2/3=2/3
x=2/3:2=1/3
1) \(a+\left(-37\right)=-23-37=-60\)
2) \(\left|-345\right|+c=345+65=410\)
Thank you Mafia nha
Chuc ban nam ms zui ze nha