Đáp án:
Bài `1:`
`a) = 5`
`b) = -77/20`
`c) = 4/5`
`2b)` $\left\{\begin{matrix}x=11& \\y=17&\\ z=23& \end{matrix}\right.$
Giải thích các bước giải:
Bài `1:`
`a) 4/3+11/3=(4+11)/3=15/3=5`
`b) -3/4: 5/11 - 1/4 : 5/11`
`=-3/4 . 11/5 - 1/4 . 11/5`
`= 11/5 . (-3/4 - 1/4)`
`= 11/5 . -7/4`
`= -77/20`
`c) (5^5. 20^6)/(25^6. 4^5)`
`=(5^5. 2^12. 5^6)/(5^12. 2^10)`
`=(5^11. 2^12)/(5^12. 2^10)`
`=(2^2)/5=4/5`
`2. b) `
`(x-1)/2=(y-2)/3=(z-3)/4`
`=> (2x-2)/4=(3y-6)/9=(z-3)/4`
`=(2x-2+3y-6-z+3)/(4+9-4)`
`=(50-5)/9`
`=45/9=5`
`=>`
$\left\{\begin{matrix}\dfrac{x-1}{2}=5& \\\dfrac{y-2}{3}=5&\\ \dfrac{z-3}{4}=5& \end{matrix}\right.$ `=>` $\left\{\begin{matrix}x-1=10& \\y-2=15&\\z-3=20& \end{matrix}\right.$ `=>` $\left\{\begin{matrix}x=11& \\y=17&\\ z=23& \end{matrix}\right.$
