12/5 : 16/15 = 9/4

9/8 : 6/5 = 15/16

Chúc bạn học tốt!! ^^

c, \(\dfrac{12}{5}:\dfrac{16}{15}=\dfrac{12}{5}.\dfrac{15}{16}=\dfrac{9}{4}\)

d, \(\dfrac{9}{8}:\dfrac{6}{5}=\dfrac{9}{8}.\dfrac{5}{6}=\dfrac{15}{16}\)

c. 12/5 : 16/15

= 12/5 . 15/16

= 9/4

d. 9/8 : 6/5

= 9/8 . 5/6

= 15/16

=\(\left[\dfrac{\left(0,4.2\right)^5}{\left(0,4\right)^6}+\dfrac{2^9.2^6.3^8}{\left(3.2\right)^6.2^9}\right]=\left[\dfrac{\left(0,4\right)^5.2^5}{\left(0,4\right)^6}+\dfrac{2^6.3^8}{3^6.2^6}\right]\)

=\(\left[\dfrac{2^5}{0,4}+3^2\right]\)

=\(\left[80+9\right]=89\)

\(\left[\dfrac{\left(2.0,4\right)^5}{0,4,0,4^5}+\dfrac{2^{15}.3^8}{3^6.2^6.2^9}\right]\div\dfrac{3^{20}.5^{30}}{3^{15}.5^{30}}\)

\(=\left[\dfrac{2^5.0.4^5}{0,4.0,4^5}+\dfrac{2^{15}.3^8}{3^6.2^{15}}\right]\div3^5\)

\(=\left[\dfrac{2^5}{0,4}+3^2\right]\div243\)

\(=80+\left(3^5\div3^2\right)\)

\(=80+3^3\)

\(=80+27\)

\(=107\)

a) \(\frac{15^5.10^5}{6^6.25^6}\)= (15.10)^5/(6.25)^6=150^5/150^6=1/150

\(^{\frac{\left(5^4-5^3\right)^3}{125^4}=\frac{\left[5^3\cdot\left(5-1\right)\right]^3}{\left(5^3\right)^4}=\frac{\left[5^3\cdot4\right]^3}{5^3\cdot4}=\frac{\left(5^3\right)^3\cdot4^3}{5^{12}}=\frac{5^9\cdot4^3}{5^9\cdot5^3}=\frac{4^3}{5^3}}\)

\(a,\dfrac{15^3}{5^4}\)

\(=\dfrac{\left(3\cdot5\right)^3}{5^4}\)

\(=\dfrac{3^3\cdot5^3}{5^4}\)

\(=\dfrac{3^3}{5}\)

\(=\dfrac{27}{5}\)

\(---\)

\(b,\dfrac{21^3}{7^4}\)

\(=\dfrac{\left(3\cdot7\right)^3}{7^4}\)

\(=\dfrac{3^3\cdot7^3}{7^4}\)

\(=\dfrac{3^3}{7}\)

\(=\dfrac{27}{7}\)

\(---\)

\(c,\dfrac{6^6}{3^8}\)

\(=\dfrac{\left(2\cdot3\right)^6}{3^8}\)

\(=\dfrac{2^6\cdot3^6}{3^8}\)

\(=\dfrac{2^6}{3^2}\)

\(=\dfrac{64}{9}\)

#\(Toru\)

\(\dfrac{2}{\sqrt[]{6}-2}+\dfrac{2}{\sqrt[]{6}+2}+\dfrac{5}{\sqrt[]{6}}\)

\(=\dfrac{2}{\sqrt[]{6}-2}+\dfrac{2}{\sqrt[]{6}+2}+\dfrac{5\sqrt[]{6}}{6}\)

\(=\dfrac{12\left(\sqrt[]{6}+2\right)}{6\left(\sqrt[]{6}-2\right)\left(\sqrt[]{6}+2\right)}+\dfrac{12\left(\sqrt[]{6}-2\right)}{6\left(\sqrt[]{6}-2\right)\left(\sqrt[]{6}+2\right)}+\dfrac{5\sqrt[]{6}\left(\sqrt[]{6}-2\right)\left(\sqrt[]{6}+2\right)}{6\left(\sqrt[]{6}-2\right)\left(\sqrt[]{6}+2\right)}\)

\(=\dfrac{12\sqrt[]{6}+24+12\sqrt[]{6}-24+5\sqrt[]{6}\left(6-2\right)}{6\left(6-2\right)}\)

\(=\dfrac{24\sqrt[]{6}+20\sqrt[]{6}}{24}\)

\(=\dfrac{44\sqrt[]{6}}{24}\)

\(=\dfrac{11\sqrt[]{6}}{6}\)

bài này mà cx đi hỏi má

\(B=\left(\dfrac{4}{1-\sqrt{5}}+\dfrac{1}{2+\sqrt{5}}-\dfrac{4}{3-\sqrt{5}}\right)\left(\sqrt{5}-6\right)\)

\(B=\left[\dfrac{4\left(1+\sqrt{5}\right)}{\left(1-\sqrt{5}\right)\left(1+\sqrt{5}\right)}+\dfrac{2-\sqrt{5}}{\left(2+\sqrt{5}\right)\left(2-\sqrt{5}\right)}-\dfrac{4\left(3+\sqrt{5}\right)}{\left(3-\sqrt{5}\right)\left(3+\sqrt{5}\right)}\right]\left(\sqrt{5}-6\right)\)

\(B=\left[\dfrac{4\left(1+\sqrt{5}\right)}{1-5}+\dfrac{2-\sqrt{5}}{4-5}-\dfrac{4\left(3+\sqrt{5}\right)}{9-5}\right]\left(\sqrt{5}-6\right)\)

\(B=\left[-\dfrac{4\left(1+\sqrt{5}\right)}{4}-\dfrac{2-\sqrt{5}}{1}-\dfrac{4\left(3+\sqrt{5}\right)}{4}\right]\left(\sqrt{5}-6\right)\)

\(B=\left(-1-\sqrt{5}-2+\sqrt{5}-3-\sqrt{5}\right)\left(\sqrt{5}-6\right)\)

\(B=\left(-\sqrt{5}-6\right)\left(\sqrt{5}-6\right)\)

\(B=-\left(\sqrt{5}+6\right)\left(\sqrt{5}-6\right)\)

\(B=-\left(5-36\right)\)

\(B=-\left(-31\right)\)

\(B=31\)

_____________________________

\(\sqrt{48}-\dfrac{\sqrt{21}-\sqrt{15}}{\sqrt{7}-\sqrt{5}}+\dfrac{2}{\sqrt{3}+1}\)

\(=4\sqrt{3}-\dfrac{\sqrt{3}\left(\sqrt{7}-\sqrt{5}\right)}{\sqrt{7}-\sqrt{5}}+\dfrac{2\left(\sqrt{3}-1\right)}{\left(\sqrt{3}-1\right)\left(\sqrt{3}+1\right)}\)

\(=4\sqrt{3}-\sqrt{3}-\dfrac{2\left(\sqrt{3}-1\right)}{2}\)

\(=3\sqrt{3}-\sqrt{3}+1\)

\(=2\sqrt{3}+1\)

\(a,\dfrac{-8}{15}+\dfrac{13}{30}-\dfrac{5}{12}=\dfrac{-32}{60}+\dfrac{26}{60}-\dfrac{25}{60}=-\dfrac{31}{60}\\ b,\dfrac{3}{2}.\dfrac{7}{2}+\left(\dfrac{-5}{6}+\dfrac{1}{10}:\dfrac{11}{30}\right)=\dfrac{21}{4}+\left(\dfrac{-5}{6}+\dfrac{3}{11}\right)=\dfrac{21}{4}+\dfrac{-37}{66}=\dfrac{619}{132}\)

\(c,\dfrac{-20}{21}.\dfrac{22}{35}+\dfrac{-20}{21}.\dfrac{13}{35}+\dfrac{-22}{21}=\dfrac{-20}{21}\left(\dfrac{22}{35}+\dfrac{13}{35}\right)+\dfrac{-22}{21}=\dfrac{-20}{21}.1+\dfrac{-22}{21}=\dfrac{-20}{21}+\dfrac{-22}{21}=\dfrac{-42}{21}=-2\)

\(\frac{15^5.10^5}{6^6.25^6}\)

\(=\frac{3^5.5^5.2^5.5^5}{3^6.2^6.5^{12}}\)

\(=\frac{3^5.2^5.5^{10}}{3^6.2^6.5^{12}}\)

\(=\frac{1}{3.2.5^2}\)

\(\frac{\left(5^4.5^3\right)^3}{125^4}\)

\(=\frac{\left(5^7\right)^3}{5^{12}}\)

\(=\frac{5^{21}}{5^{12}}\)

\(=5^9\)

tính lũy thừa nha bn 

Lời giải:

\(\left(\frac{15}{\sqrt{6}+1}+\frac{4}{\sqrt{16}-2}-\frac{12}{3-\sqrt{16}}\right).(\sqrt{6}+11)=\left(\frac{15(\sqrt{6}-1)}{(\sqrt{6}+1)(\sqrt{6}-1)}+\frac{4}{4-2}-\frac{12}{3-4}\right)(\sqrt{6}+11)\)

\(=\left(\frac{15(\sqrt{6}-1)}{6-1}+2+12\right)(\sqrt{6}+11)=(3\sqrt{6}-3+14)(\sqrt{6}+11)\)

\(=(3\sqrt{6}+11)(\sqrt{6}+11)\)