Đáp án:
Giải thích các bước giải:
Bài 1:
a, 35%: 2 1/3- 0,3: 1 5/7= 7/20: 7/3- 3/10: 12/7
= 3/20- 7/40= 6/40- 7/40= -1/40
b, 1/3+ 1 3/4- ( 1 3/4- 80%)= 1/3+( 1 3/4- 1 3/4) +4/5= 1/3+ 0+ 4/5= 5/15+ 12/15= 17/15= 1 2/15
c, (-2)^3. (3/4-0,25): (2 1/4- 1 1/6)= -8. (3/4- 1/4): (9/4- 7/6)= -8. 1/2: ( 27/12- 14/12)= -4: 13/12= -48/13
d, 125%.( -1/2)^2: (1 5/16- 1,5)+ 2020^0= 5/4. 1/4: (21/16- 24/16)+1= 5/16: -3/16+1= -5/3+1= 2/3
Bài 2:
F= 4/ 2.4+ 4/4.6+ 4/6.8+ ...+4/2018.2020= 2.( 2/2.4+ 2/4.6+...+2/2018.2020)= 2.( 1/2-1/4+1/4-1/6+....+1/2018-1/2020)= 2.(1/2- 1/201/8)= 2.504/509= 1008/209
=> Vậy F= 1008/2009
Bài 3
60%x + 2/3x= 1/3.6 1/3
3/5.x+ 2/3.x= 1/3.19/3
19/15.x= 19/9
x= 19/9: 19/15
x= 5/3
Vậy x=5/3
1/3.x+ 2/5.(x-1)=0
1/3.x+ 2/5.x- 2/5=0
11/15.x= 2/5
x= 2/5: 11/15
x= 2/11
Vậy x= 2/11
Chúc bạn học tốt