=0.54545454545 nha 

\(1-\dfrac{5}{14}-\dfrac{5}{84}-\dfrac{5}{204}-\dfrac{5}{374}\) =\(1-\left(\dfrac{1}{1.14}+\dfrac{1}{14.6}+\dfrac{1}{6.34}+\dfrac{1}{34.11}\right)\)

= \(1-\left(\dfrac{1}{1}-\dfrac{1}{14}+\dfrac{1}{14}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{34}+\dfrac{1}{34}-\dfrac{1}{11}\right)\)

= 1 - \(\left(1-\dfrac{1}{11}\right)\) = \(1-\dfrac{10}{11}=\dfrac{1}{11}\)

\(=1-\dfrac{5}{2\cdot7}-\dfrac{5}{7\cdot12}-\dfrac{5}{12\cdot17}-\dfrac{5}{17\cdot22}\)

\(=1-\left(\dfrac{1}{2}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{12}+\dfrac{1}{12}-\dfrac{1}{17}+\dfrac{1}{17}-\dfrac{1}{22}\right)\)

\(=5-\dfrac{11-1}{22}=5-\dfrac{10}{22}=5-\dfrac{5}{11}=\dfrac{50}{11}\)

b,1×2×3×...×9-1×2×3×...×8-1×2×3×...×7×8^2

=(1×2×3×...×8)×(9-1-8)

=(1×2×3×...×8)×0

=0

Bài 1:

A,

(100+121+144)÷(169+196)

=365:365=1

B

,1.2.3...7.8.(9-1-8)

=1.2.3...7.8.0=0

C,

3^2.2^4.2^32/11.2^13.2^22-2^26

=3^2.2^36/11.2^35-2^36

=3^2.2^36/2^35-(11-2)

=9.2/9=2

D,

=1152-374-1152+(-65)+374

=(1152-1152)+(-374+374)+(-65)

=0+0+(-65)=-65

E,

=13-(12-11-10+9)+(8-7-6+5)-(4-3-2+1)

=13-0+0-0=13

Bài 2:

A,(19x+50)÷14=25-16

(19x+50)÷14=9

19x+50=126

19x=76

x=4

B,

31x+(1+2+3+...+30)=1240

31x+465=1240

31x=775

×=25

BÀI 2:

c)11-(-53+x)=97

=> x=97-11-53

=> x=33

K CHO MÌNH NHA