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a) (x – 45).27 = 0 ó x – 45 = 0 ó x = 45
b) 41.(2x – 8).13 = 0 ó 2x – 8 = 0 ó x = 4
c) (x – 36):18 = 12 ó x – 36 = 12.18 ó x = 216 + 36 ó x = 252
d) 43.(x – 18) = 86 ó x – 18 = 86:43 ó x = 2+18 ó x = 20
e) 96 : (121 – x) = 4 ó 121 – x = 96 : 4 ó 121 – x = 24 ó x = 121 – 24 ó x = 97
f) 340 : (15x+5) = 17 ó 15x + 15 = 340 :17 ó 15x + 5 = 20 ó 15x = 20 – 5 ó 15x = 15 ó x = 1
b/ =-36.16+36.41-16.41+16.36
=36.41-16.41
=41.(36-16)
=41.20
=820
a.
= -30-15+21-30-15-9
= (-30 - 30)+(-15-15)+(21-9)
= -60 -30 + 12
= -78
b.
= (6-18)+(-5+4)+(-20+21)
= 12 + (-1) + 1
=12
c.
= 27.(19+31)
=27. 50
= 1350
d.
= (-25).(64+36)
= -25 . 100
= -2500
e. 18.36 + 72.15
= 18.36 + 4.18.15
=18.( 36 + 60)
= 18.96
= 1728
Bài 2:
a) \(\left(x-34\right).15=30\)
\(\Rightarrow x-34=2\)
\(\Rightarrow x=36\)
Vậy \(x=36\)
b) \(18\left(x-16\right)=18\)
\(\Rightarrow x-16=1\)
\(\Rightarrow x=17\)
Vậy \(x=17\)
a) 86 + 357 + 14
= (86 + 14) + 357
= 100 + 357
= 457
b) 72 + 69 + 128
= (72 + 128) + 69
= 200 + 69
= 269
c) 25 . 5 . 4 . 27 . 2
= (25 . 4) . (2 . 5) . 27
= 100 . 10 . 27
= 1000 . 27
= 27000
d) 28 . 64 + 28 . 36
= 28 . (64 + 36)
= 28 . 100
= 2800
2. Tìm số tự nhiên x ,biết
a) ( x - 34 ) . 15 = 30
(x - 34) = 30 : 15
(x - 34) = 2
x = 2 + 34
x = 36.
b) 18 . ( x - 16 ) = 18
( x - 16 ) = 18 : 18
( x - 16 ) = 1
x = 1 + 16
x = 17.
Câu 3:
a) \(\dfrac{12}{36}=\dfrac{12:12}{36:12}=\dfrac{1}{3}\)
\(\dfrac{-16}{20}=\dfrac{-16:4}{20:4}=\dfrac{-4}{5}\)
b) \(\dfrac{21}{105}=\dfrac{21:21}{105:21}=\dfrac{1}{5}\)
\(\dfrac{35}{150}=\dfrac{35:5}{150:5}=\dfrac{7}{30}\)
Câu 4:
a) \(\dfrac{3}{10}+\dfrac{5}{10}=\dfrac{3+5}{10}=\dfrac{8}{10}=\dfrac{4}{5}\)
b) Ta có: \(\left(-27\right)\cdot36+64\cdot\left(-27\right)+23\cdot\left(-100\right)\)
\(=\left(-27\right)\cdot\left(64+36\right)+23\cdot\left(-100\right)\)
\(=-27\cdot100-23\cdot100\)
\(=100\left(-27-23\right)\)
\(=-50\cdot100=-5000\)
c) \(\dfrac{5}{8}+\dfrac{3}{12}=\dfrac{15}{24}+\dfrac{6}{24}=\dfrac{21}{24}=\dfrac{7}{8}\)
d) Ta có: \(\dfrac{-2}{17}+\dfrac{3}{19}+\dfrac{-15}{17}+\dfrac{16}{19}+\dfrac{5}{6}\)
\(=\left(-\dfrac{2}{17}+\dfrac{-15}{17}\right)+\left(\dfrac{3}{19}+\dfrac{16}{19}\right)+\dfrac{5}{6}\)
\(=-1+1+\dfrac{5}{6}\)
\(=\dfrac{5}{6}\)
a) 135 . (-27) + 27 . 235
= 27 . (235 - 135)
= 27 . 100
= 2700
b) 36 . (-125) - 125 . (-46)
= 125 . (-36 + 46)
= 125 . 10
= 1250
c) 32 . (-64) - 64 . 68
= 64.(-32 - 68)
= 64.(-100)
= -6400
d) (145 - 45) . (-31) + 31 . (-100)
= 100 . (-31) + 31.(-100)
= 100.(-31 - 31)
= 100.(-62)
= -6200
a)
=(-135)x27+27x235
=27x[+(235+135)]
=27x31725
=856575
b)
=(-36)x125-125x(-46)
=125x[-(36+46)]
=125x(-1656)
=-207000
c)
=(-32)x64-64x68
=64x[-(68-32)]
=64x(-36)
=-(64x36)
=-2304
d)
=100x(-31)+31x(-100)
=(-100)x31+31x(-100)
=31x[-(100+100)]
=31x(-200)
=-(31x200)
=-6200
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