Đáp án:
Bài `1:`
`a) 1/2-4/7. 1/4-|-8|+2020`
`=1/2-1/7-8+2020`
`=5/14-8+2020`
`= -107/14+2020`
`= 28173/14`
`b) 3/7.(2/5-1/4)+3/7.(1/3+1/4)`
`=3/7(2/5-1/4+1/3+1/4)`
`=3/7. 11/15`
`=11/35`
`c) (45^20. (5^20)^3)/(75^40)`
`=((3^2. 5)^20 . 5^60)/((3.5^2)^40)`
`=(3^40. 5^20. 5^60)/(3^40. 5^80)`
`=1`
`d) (1/11-5/45):2021/2020+2020/2021.(-40/45+11/10)`
`=(1/11-1/9).2020/2021+2020/2021.(-8/9+11/10)`
`=2020/2021.(1/11-1/9-8/9+11/10)`
`=2020/2021. 21/110`
`=4242/22231`
Bài `2:`
`a) 7/12- (3/8-x)=-5/6`
`-> 7/12-3/8+x=-5/6`
`-> 5/24+x=-5/6`
`-> x=-5/6-5/24`
`-> x=-25/24`
`b) (x+2/3)^2=9/16`
`->(x+2/3)^2=(+-3/4)^2`
`->` \(\left[ \begin{array}{l}x+\dfrac{2}{3}=\dfrac{3}{4}\\x+\dfrac{2}{3}=\dfrac{-3}{4}\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=\dfrac{1}{12}\\x=\dfrac{-17}{12}\end{array} \right.\)
`c) 4-|2x-3/4|=1/12`
`-> |2x-3/4|=4-1/12=47/12`
`->` \(\left[ \begin{array}{l}2x-\dfrac{3}{4}=\dfrac{47}{12}\\2x-\dfrac{3}{4}=\dfrac{-47}{12}\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=\dfrac{7}{3}\\x=\dfrac{-19}{12}\end{array} \right.\)
