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2. tìm số tự nhiên x , biết
A. 3x - 14 = 25 : 23
3x - 14 = 25-3
3x-14 = 22
3x - 14 = 4
3x = 4 + 14
3x = 18
x = 18: 3
x = 6
B. 150 - 2 . ( x + 2 ) = 4 . 22
150 - 2 ( x + 2 ) = 22 . 22
150 - 2 (x + 2) = 22+2
150 - 2 (x+2 ) = 24
150-2 (x+2 ) = 16
2 ( x+2 ) = 150 - 16
2 (x+2) = 134
x+2 = 134 : 2
x +2 =67
x = 65
4. so sánh 5 200 và 2 500
\(2^{500}=\left(2^5\right)^{100}=23^{100}\)
\(5^{200}=\left(5^2\right)^{100}=25^{100}\)
Vì \(23< 25\) nên:
\(\Rightarrow23^{100}< 25^{100}\)
Vậy : \(5^{200}>2^{500}\)
a) 36 : 32 + 23 . 22
= 34 + 25
= 81 + 32
= 113
b) (39 . 42 - 37 . 42) : 42
= 42 . (39 - 37) : 42
= 2
a)36:32+23.22
=\(3^{6-2}+2^{3+2}=3^4+\)\(2^5\)
=81 + 32 = 113
b) \(\left(39.42-37.42\right):42=42\left(39-37\right):42\)=2
c) \(5.4^2-18:3^2=5.16-18:9=80-2=78\)
d) \(80-\left[130-\left(12-4\right)^2\right]=80-\left(130-8^2\right)=80-\left(130-64\right)\)
= 80 - 66=14
a) 12 : { 400 : [500 – (125 + 25 . 7)]}
=12 : { 400 : [500 – (125 + 175)]}
=12 : [ 400 : [500 – 300)]
=12 : (400:200)
=12:2=6
b) 5 . 22 – 18 : 3
=5.4-6
=20-6=14
c) 18 : 3 + 182 + 3.(51 : 17)
=5+182+3.3
=187+9=196
d) 25 . 8 – 12.5 + 170 : 17 – 8
=200-60+10-8
=142
e) 2.52+ 3: 710 – 54: 33
=2.25+3:1-54:27
=50+3-2
=51
f) 189 + 73 + 211 + 127
=(189+211)+(73+127)
=400+200=600
g) 375 : {32 – [ 4 + (5. 32– 42)]} – 14 )
=375 : {32 – [ 4 + (160– 42)]} – 14 )
=375 : [32 – ( 4 + 118) – 14 ]
=375:(32-122-14)
=375:-104
=-375/104
h) (52022 + 52021) : 52021
=(52022:52021)+(52021:52021)
=5+1=6
a) 23 . 17 - 23 . 14
= 23(17-14)
=23. 3= 24
b) 80 - ( 4 . 5 - 3 . 23 )
= 80- 22. (5-3.2)= 80- 22.(-1)
= 80- 4.(-1)= 80- (-4)= 84
c) 35 - { 12 - [ -14 + ( -2) }
= 35 - { 12 - (-16) }
=35- 28= 7
d) 49 - ( -45) - 23
= 94-23= 71
e) 13 - 18 - ( -42) - 15
= -5 -(-42) -15
= -20+42= 22
g) -452 - ( -67 + 75 - 452 )
= -452- (8-452)
= -452 -(- 444)= -8
h) |31−17|−|13−52|
= 14- 39= -25
80 -(4.52 -3.23)
= 80- (4.25- 3.8)
= 80- (100-24)
= 80-76= 4
b, (39. 42 - 37 . 42 ) : 42
= [ 42 ( 39 - 37 ) ] : 42
= 2 . 42 : 42
= 2
a, 2^3.17-2^3.14
= 2^3.(17-14)
= 2^3. 3
= 8.3=24
b, 80-[30-(5-1)^2]
=80-[30-16]
=80-4
=76
c,3^4+2^5
=81+32
=113
d,3.5^2+16:2^2
=3.25+16:4
=75+4
=79
e,(39.42+37.42):42
=[42.(39+37)]:42
=[42.76]:42
=42.76:42
=76