0,(57)=0,(01).57 = \(\frac{1}{99}.57=\frac{19}{33}\)

0,(42)=0,(01).42=\(\frac{1}{99}.42=\frac{14}{33}\)

=>0,(57)+0,(42)=\(\frac{19}{33}+\frac{14}{33}=\frac{33}{33}=1\)

Vậy 0,(57)+0,)42)=1

a) 0,(5)+0,(3)+0,(1)

=\(\frac{5}{9}\)+\(\frac{1}{3}\)+\(\frac{1}{9}\)

=\(\frac{5}{9}\)+\(\frac{3}{9}\)+\(\frac{1}{9}\)

=\(\frac{5+3+1}{9}\)

=\(\frac{9}{9}\)

=1

b) 0,(57)+0,(42)

=\(\frac{19}{33}\)+\(\frac{14}{33}\)

=\(\frac{19+14}{33}\)

=\(\frac{33}{33}\)

=1

Chúc cậu học tốt •ω•

a/ 0,(5) + 0,(3) + 0,(1) = 1

b/ 0,(57) + 0,(42) = 1

a: \(\dfrac{2032-x}{25}+\dfrac{2053-x}{23}+\dfrac{2070-x}{21}+\dfrac{2083-x}{19}-10=0\)

\(\Leftrightarrow\left(\dfrac{2032-x}{25}-1\right)+\left(\dfrac{2053-x}{23}-2\right)+\left(\dfrac{2070-x}{21}-3\right)+\left(\dfrac{2083-x}{19}-4\right)=0\)

=>2007-x=0

hay x=2007

b: \(\Leftrightarrow x+\left(1+1+1+1+1+1+1\right)+\left(\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}+\dfrac{1}{72}+\dfrac{1}{90}\right)=0\)

\(\Leftrightarrow x+7+\left(\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+...+\dfrac{1}{9}-\dfrac{1}{10}\right)=0\)

=>x+7+1/3-1/10=0

hay x=-217/30

Bn ơi bn ko đánh số vào từng góc kìa

ờ để mk lm lại 

x-y-z=0

=> x=y+z

y=x-z

-z=y-x

B=(1-z/x)(1-x/y)(1+y/z)

B=((x-z)/x)((y-x)/y)((z+y)/z)

B=(y/x)(-z/y)(x/z)

B=(-zyx)/(xyz)

B=-1

( -3/4 )²                   ;  ( -0,5 )²           ;  (9,7 )^0

= 9/16                    ;   = 1/4             ; = 1

( -2/5 )³                   ;  ( -0,5 )³

= -8/125                  ;  = -1/8