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![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=\dfrac{5}{7}.\dfrac{5}{11}+\dfrac{5}{7}.\dfrac{8}{11}-\dfrac{5}{7}.\dfrac{2}{11}\)
\(A=\dfrac{5}{7}.\left(\dfrac{5}{11}+\dfrac{8}{11}-\dfrac{2}{11}\right)\)
\(A=\dfrac{5}{7}.\dfrac{5+8-2}{11}\)
\(A=\dfrac{5}{7}.\dfrac{11}{11}\)
\(A=\dfrac{5}{7}.1=\dfrac{5}{7}\)
\(B=\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{35}+\dfrac{1}{42}+\dfrac{1}{56}+\dfrac{1}{63}\)
\(B=\dfrac{95}{72}\)
\(C=\dfrac{4^6.9^5+6^9.120}{8^4-3^{12}-6^{11}}\)
\(C=\dfrac{\left(2^2\right)^3.\left(3^2\right)^5+\left(2.3\right)^9.2^3.3.5}{\left(2^3\right)^4.3^{12}-\left(2.3\right)^{11}}\)
\(C=\dfrac{2^{12}.3^{10}+2^9.3^9.2^3.3.5}{2^{12}.3^{12}-2^{11}.3^{11}}\)
\(C=\dfrac{2^{12}.3^{10}.\left(1+5\right)}{2^{11}.3^{11}.5}\)
\(C=\dfrac{2.6}{5.3}=\dfrac{12}{15}=\dfrac{4}{5}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a/ A= 1-3+5-7+9-11+......+97-99
= -2+(-2)+(-2)+......+(-2)
= (-2).25=-50
b/B=-1-2-3-4-...-100
=-(1+2+3+4+...+100)
=-5050
c/C=1-2+3-4+5-6+......+99-100
= -1+(-1)+(-1)+.............+(-1)
=(-1).50=-50
d/D=1-2-3+4+5-6-7+8+9-....+94-95
= (1-2-3+4)+(5-6-7+8)+.......+(92-93-94+95)
= 0+0+0+...+0=0
![](https://rs.olm.vn/images/avt/0.png?1311)
a) A = ( -1,5 ) . 2 2/3 . 1/6 . ( 4/7 - 2/5 ) : 1 1/35=-1
B = [( 82/128 + 3/4 ) : 1 3/16 ]/1 11/19=380/1443
k nha
A = -5/11 + ( -6/11 +1)
A = -5/11 + ( -6/11 + 11/11 )
A = -5/11 + 5/11
A = 0/11
B = 2/3 + ( 5/7 + -2/3 )
B = 2/3 + ( 15/21 + -14/21 )
B = 2/3 + 1/21
B = 14/21 + 1/21
B = 15/21
B = 5/7
C = ( -1/4 + -5/8 ) + -3/8
C = ( -2/8 + -5/8 ) + -3/8
C = -7/8 + -3/8
C = -10/8
C = -5/4