Bài 1 : Tính
a)(-69). /3 – 7/ – 31 . /16 – 20/
b)(-4)2 : [ 17 – (24 – 27)2 ]
c)-(-347) + (-40) + /-2021/ – /+307/
Bài 2: Tìm x :
a)10 – 3 . (1 – x) = (-5)
b)17 – 3x = (-10)
c)(-49) – (17 + x) = /-38/
Bài 1 : Tính
a)(-69). /3 – 7/ – 31 . /16 – 20/
b)(-4)2 : [ 17 – (24 – 27)2 ]
c)-(-347) + (-40) + /-2021/ – /+307/
Bài 2: Tìm x :
a)10 – 3 . (1 – x) = (-5)
b)17 – 3x = (-10)
c)(-49) – (17 + x) = /-38/
Đáp án:
-400
Giải thích các bước giải:
Bài 1:
1. \(\begin{array}{l}
– 69.|3 – 7| – 31.|16 – 20|\\
= – 69.4 – 31.4\\
= – 4(69 + 31) = – 4.100 = – 400
\end{array}\)
2. \(\begin{array}{l}
( – 4).2:{\rm{[}}17 – (24 – 27).2)\\
= – 8:{\rm{[}}17 – ( – 3).2]\\
= – 8:(17 + 6) = – 8:23 = \frac{{ – 8}}{{23}}
\end{array}\)
3. \(\begin{array}{l}
– ( – 347) + ( – 40) + | – 2021| – | + 307|\\
= 347 – 40 + 2021 – 307\\
= (347 – 40 – 307) + 2021 = 2021
\end{array}\)
Bài 2:
1. \(\begin{array}{l}
10 – 3(1 – x) = – 5\\
\Leftrightarrow 3(1 – x) = 10 + 5 = 15\\
\Leftrightarrow 1 – x = 15:3 = 5\\
\Leftrightarrow x = 1 – 5 = – 4
\end{array}\)
2. \(\begin{array}{l}
17 – 3x = – 10\\
\Leftrightarrow 3x = 17 + 10 = 27\\
\Leftrightarrow x = 27:3 = 9
\end{array}\)
3. \(\begin{array}{l}
– 49 – (17 + x) = | – 38|\\
\Leftrightarrow – 49 – (17 + x) = 38\\
\Leftrightarrow 17 + x = – 49 – 38 = – 87\\
\Leftrightarrow x = – 87 – 17 = – 104
\end{array}\)
Đáp án:
bài 1
a) (-69)./3-7/-31./16-20/
=(-69)./-4/-31./-4/
=(-69).4 – 31.4
=[(-69)-31)] .4
=(-100).4
=-400
b)(-4).2 : [17 – (24 – 27).2]
=8:[17 – (-3).2]
=8: [17 -9]
=8 : 8
=1
c)-(-347)+ (-40) + /-2021/ – /+307/
= 347+ (-40) + 2021 – 307
= 307+ 1714
=2021
2/
a) 10 – 3.(1-x)=(-5)
3.(1-x)=10- (-5)
3. (1-x)=15
1-x=15:3
1 – x = 5
x= 1- 5
x=-4
b) 17 – 3x =(-10)
3x=17-(-10)
3x = 27
x = 27 : 3
x = 9
c) (-49) – (17 +x) = /-38/
(-49) – (17+x) = 38
17+x =(-49) – 38
17 + x= -87
x= (-87) – 17
x=-104
Vote cho mình năm sao đi