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