a, 5/-14. 7/-19=8/38

b, -15/4 .( 16/-25 )=12/5

c, 3/-10 .( -15/-2 )=

d, -5/7 . ( 21/-10 )=-9/4

e, 10/-3. (6/-5)==4

f, 21/-9 . ( -6/14 )=1

g, -10/9 . ( 36/20 )=-2

em hong có bít∞❤

a: \(=\dfrac{18+6}{27+6}=\dfrac{24}{33}=\dfrac{8}{11}\)

b: \(=\dfrac{21\cdot7\cdot11}{3\cdot11\cdot4}=\dfrac{147}{12}=\dfrac{49}{4}\)

a)  $\frac{3}{5} \times \frac{6}{7} = \frac{{3 \times 6}}{{5 \times 7}} = \frac{{18}}{{35}}$                                                 

 b) $\frac{2}{9} \times \frac{{18}}{3} = \frac{{2 \times 18}}{{9 \times 3}} = \frac{{36}}{{27}} = \frac{4}{3}$

c)  $\frac{5}{7} \times 12 = \frac{{5 \times 12}}{7} = \frac{{60}}{7}$                                            

d)  $21 \times \frac{2}{7} = \frac{{21 \times 2}}{7} = \frac{{42}}{7} = 6$

1. -28 + 32

2. 50 + 21

3. (-45) + (-30)

4. x + (-80)

5. 7 + (-a)

6. -25 + a

a, -49

b, 25

c, 40

d, -88

a) (-10)-21-18=-(10+21+18)=-49

b) 24-(-16)+(-15)=24+16-15=40-15=25

c) 49-[15+(-6)]=49-9=40

d) (-44)-[(-14)-30]=-44-(-44)=0

a, -49

b, 25

c, 40

d, -88

Lời giải:
\((\frac{3}{7})^{21}:(\frac{9}{49})^6=(\frac{3}{7})^{21}:[(\frac{3}{7})^2]^{6}=(\frac{3}{7})^{21}:(\frac{3}{7})^{12}\\ =(\frac{3}{7})^{21-12}=(\frac{3}{7})^9\)

21 x= 45

21 x 

= 45

// =.= \\

​(3/7)^21 : (9/49)^6 = (3/7)^21 : (3/7 *3/7)^6= (3/7)^21 : (3/7)^12 = 3/7^9

( 3/7) ⁹

(3/7)^21:(9/49)^6

=(3/7)^21:[(3/7)^2]^6

=(3/7)^21:(3/7)^12

=(3/7)^9

(3/7)^21:[(3/7)^2]^6

(3/7)^21:[(3/7)^12

(3/7)^21-12

^{(3/7)^9}

(3/7)²¹: (9/49)⁶

= (3/7)²¹: (3²/7²)⁶

= (3/7)²¹: (3/7)¹²

= (3/7)^21-12

= (3/7)⁹

=(3/7)^9 lol