làm hộ nha

Mk làm lun nhé

a)  =>-5*9=15*2x                       b) =>4/8x=-11/2-7/3                     c) =>-1/4+-4/13:x=-5                          d) =>x(3+7/3)=1/5

     =>-45=15*2x                             =>4/8x=-47/6                               =>-4/13:x=-19/4                                  =>16/3x=1/5

     =>2x=-3                                    =>x=-47/3                                    =>x=16/247                                         =>x=3/80

     =>x=-3/2  

Bài làm

a) \(-\frac{5}{2x}=\frac{15}{9}\)

\(\Rightarrow2x=-\frac{5.9}{15}=-3\)

\(\Rightarrow x=-\frac{3}{2}\)

Vậy x = \(x=-\frac{3}{2}\)

b) \(\frac{7}{3}+\frac{4}{8}x=-\frac{11}{2}\)

\(\Rightarrow\frac{4}{8}x=-\frac{11}{2}-\frac{7}{3}\)

\(\Rightarrow\frac{4}{8}x=-\frac{33}{6}-\frac{14}{6}\)

\(\Rightarrow\frac{4}{8}x=-\frac{47}{6}\)

\(\Rightarrow x=-\frac{47}{6}.\frac{8}{4}\)

\(\Rightarrow x=-\frac{47}{3}\)

Vậy \(x=-\frac{47}{3}\)

c) \(-\frac{1}{4}+\frac{-4}{13}:x=-\frac{8}{6}+\frac{11}{-3}\)

\(\Rightarrow-\frac{1}{4}+\frac{-4}{13}:x=-\frac{8}{6}+\frac{22}{-6}\)

\(\Rightarrow-\frac{1}{4}+\frac{-4}{13}:x=-5\)

\(\Rightarrow\frac{-4}{13}:x=-5-\left(-\frac{1}{4}\right)\)

\(\Rightarrow-\frac{4}{13}:X=-\frac{20}{4}+\frac{1}{4}\)

\(\Rightarrow-\frac{4}{13}:X=-\frac{21}{4}\)

\(\Rightarrow X=-\frac{4}{13}:-\frac{21}{4}\)

\(\Rightarrow X=-\frac{4}{13}.\frac{-4}{21}\)

\(\Rightarrow X=\frac{16}{273}\)

Vậy ....

s) \(3x+\frac{7}{3}x=\frac{1}{5}\)

\(\Rightarrow x\left(3+\frac{7}{3}\right)=\frac{1}{5}\)

\(\Rightarrow x\left(\frac{9}{3}+\frac{7}{3}\right)=\frac{1}{5}\)

\(\Rightarrow x.\frac{16}{3}=\frac{1}{5}\)

\(\Rightarrow x=\frac{1}{5}.\frac{3}{16}\)

\(\Rightarrow x=\frac{3}{80}\)

Vậy..

\(P=\dfrac{x+\sqrt{x}}{3\sqrt{x}-1}=\dfrac{7-4\sqrt{3}+\sqrt{7-4\sqrt{3}}}{3\sqrt{7-4\sqrt{3}}-1}=\dfrac{7-4\sqrt{3}+\sqrt{\left(2-\sqrt{3}\right)^2}}{3\sqrt{\left(2-\sqrt{3}\right)^2}-1}=\dfrac{7-4\sqrt{3}+\left|2-\sqrt{3}\right|}{3\left|2-\sqrt{3}\right|-1}=\dfrac{7-4\sqrt{3}+2-\sqrt{3}}{3\left(2-\sqrt{3}\right)-1}=\dfrac{9-5\sqrt{3}}{5-3\sqrt{3}}=\dfrac{\left(9-5\sqrt{3}\right)\left(5+3\sqrt{3}\right)}{\left(5-3\sqrt{3}\right)\left(5+3\sqrt{3}\right)}=\dfrac{45+2\sqrt{3}-45}{-2}=-\sqrt{3}\)

Thay \(x=7-4\sqrt{3}\) vào P, ta được:

\(P=\dfrac{7-4\sqrt{3}+2-\sqrt{3}}{6-3\sqrt{3}-1}\)

\(=\dfrac{9-5\sqrt{3}}{5-3\sqrt{3}}=-\sqrt{3}\)

Bài 1 :

Vì ƯCLN ( a , b ) = 14 => a = 14x ; b = 14y

Mà a + b = 42

Thay a = 14x ; b = 14y vào a + b = 42 được

14x + 14y = 42

14 . ( x + y ) = 42

=> x + y = 3

=> ( x , y ) = ( 0 ; 3 ) ; ( 3 ; 0 ) ; ( 1 ; 2 ) ; ( 2 ; 1 )

=> ( a ; b ) = ( 0 ; 42 ) ; ( 42 ; 0 ) ; ( 14 ; 28 ) ; ( 28 ; 14 )

Vậy ( a ; b ) = ( 0 ; 42 ) ; ( 42 ; 0 ) ; ( 14 ; 28 ) ; ( 28 ; 14 )

Link đây nha bạn tham khảo thử

https://sachgiaibaitap.com/sach_giai/giai-sach-bai-tap-toan-lop-6-bai-17-uoc-chung-lon-nhat/

Học tốt nhé 

⇒

Giải thích các bước giải:

 Gọi nCa=amolnCa=amol, nNa=4amolnNa=4amol

Phương trình phản ứng:

Theo phương

nH2=0,5.nNa+nCa=0,5.4a+a=3a=
6,72/22,4=0,3

⇒

mNa=4.0,1.23=9,2gmNa=4.0,1.23=9,2g

mCa=0,1.40=4gmCa=0,1.40=4g

mNaOH=4.0,1.40=16gmNaOH=4.0,1.40=16g

mdungdịchNaOH=16.100/8=200g

mhỗnhợpA=x=9,2+4=13,2g

⇒mH2O=y=200−13,2=186,8g