Tìm a nguyên sao cho:
a) 7/8 < a/2 < 40
b) 19/40 < a/4 < 65/2
c) 32/7 < a/7 < 70
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![](https://rs.olm.vn/images/avt/0.png?1311)
a) 72 + 20 = 92
68 – 40 = 28
350 + 30= 380
970 – 70 = 900
b) 411 + 300 = 7811
625 + 200 = 825
954 – 400 = 554
367 – 300 =67
c) 32 + 7 + 8 = (32+8)+7=40+7=47
54 + 7 + 3 = 54 + (7+3)= 54+10=64
1 + 16 + 9 = (1+9)+16=10+16=26
96 + 40 + 4 = (96+4)+40=100+40=140
![](https://rs.olm.vn/images/avt/0.png?1311)
a)13-2(x+1)=7
2.(x+1)=13-7
2.(x+1)=6
x+1=6/2
x+1=3
x=3-1
x=2
a, 13 - 2 ( x + 1 ) = 7
2 .( x + 1 ) = 13 - 7
2 .( x + 1 ) = 6
x + 1 = 6 : 2
x + 1 = 3
x = 3 - 1
x = 4
![](https://rs.olm.vn/images/avt/0.png?1311)
a: \(\Leftrightarrow\left(a^2-3\right)\left(a^2-10\right)< 0\)
\(\Leftrightarrow3< a^2< 10\)
\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{3}< a< \sqrt{10}\\-\sqrt{10}< a< -\sqrt{3}\end{matrix}\right.\)
d: \(\Leftrightarrow\left(a-3\right)\left(a+1\right)< 0\)
hay -1<a<3
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 1
a, 32.(-64) - 64. 68
= -64.(32 + 68)
= -64 .100
= - 6400
b, -54.76 + 12.(-76) - 76.34
= -76.(54 + 12 + 34)
= -76.100
= -7600
19- 42.(-19) + 38.5
= 19 + 42.19 + 19.2.5
= 19.(1 + 42 + 10)
= 19.53
= 1007
a: =>7/4<a<80
=>\(a\in\left\{2;3;...;79\right\}\)
b: =>19/10<a<130
=>\(a\in\left\{2;3;...;129\right\}\)
c: =>32<a<490
=>\(a\in\left\{33;34;...;489\right\}\)