làm hết à

daps an : C

(-\(\frac{4}{12}\)) +7=(\(-\frac{1}{3}\)) + 7

                 =(-\(\frac{1}{3}\))+\(\frac{21}{3}\)

                 =\(\frac{20}{3}\)

( - 4 /12 ) + 7 = ( - 1/3 ) + 7

                      = ( - 1/3 ) + 21/3 

                      = 20/3

0.0927...= 927%

Ủa, lớp 4 làm gì có câu 9 : 97 đôu??? 

B

b

hai đáp án khác nhau nên khó chọn quá !

`c)A=(9^4*27^5*3^6*3^5)/(3^8*81^4*234*8^2)`

`A=(3^8*3^15*3^11)/(3^8*3^16*3^2*2*13*2^6)`

`A=(3^34)/(3^36*2^8*13)`

`A=1/(3^2*2^8*13)`

`B=(4^6*9^5+6^9.120)/(8^4*3^12-6^11)`

`B=(2^12*3^15+2^12*3^10*5)/(2^12*3^12-2^11*3^11)`

`B=(2^12*3^10(3^5+5))/(2^11*3^11*(6-1))`

`B=(2^12*3^10*248)/(2^11*3^11*5)`

`B=(248*2)/(3*5)`

`B=496/15`

c) A = \(\dfrac{9^4.27^5.3^6.3^5}{3^8.81^4.234.8^2}=\dfrac{3^8.3^{15}.3^6.3^5}{3^8.3^{16}.2.3^2.13.2^6}=\dfrac{3^{34}}{3^{26}.2^7.13}=\dfrac{3^8}{2^7.13}\)

d)  B =\(\dfrac{4^6.9^5+6^9.120}{8^4.3^{12}-6^{11}}=\dfrac{2^{12}.3^{10}+2^9.3^9.2^3.3.5}{2^{12}.3^{12}-2^{11}.3^{11}}=\dfrac{2^{12}.3^{10}+2^{12}.3^{10}.5}{2^{11}.3^{11}\left(2.3-1\right)}=\dfrac{2^{12}.3^{10}.6}{2^{11}.3^{11}.5}=\dfrac{2.6}{3.5}=\dfrac{4}{5}\)

\(\Delta AHB=\Delta AHC\Rightarrow\widehat{AHB}=\widehat{AHC}\) (2 góc tương ứng)

Mà \(\widehat{AHB}+\widehat{AHC}=180^o\) (2 góc kề bù)

\(\Rightarrow\widehat{AHB}=\widehat{AHC}=90^o\)

\(\Rightarrow AH\perp BC\left(đpcm\right)\)

\(\Delta AHB=\Delta AHC\Rightarrow\widehat{AHB}=\widehat{AHC}\left(2.góc.tương.ứng\right)\)

Ta có:\(\widehat{AHB}+\widehat{AHC}=180^o\left(2.góc.kề.bù\right)\\ \Rightarrow2\widehat{AHB}=180^o\left(vì\widehat{AHB}=\widehat{AHC}\right)\\ \Rightarrow\widehat{AHB}=90^o\\ \Rightarrow AH\perp BC\)