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1/3 x 46 +2/3x37 3,2x (95x10) +(8x4)x 187 -(32x 10) x 8,2
=(1/3+2/3) x (46+37) 32x95+32x 187- 32x 82
= 1x 100 32x( 95+187-82)
= 100 = 32 x200
= 6400
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Gọi số sách là x
Theo đề, ta có: \(x-3\in\left\{300;600\right\}\)
hay x=303
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\(a.120=2^3.3.5\)
\(320=2^6.5\)
\(ƯC\left(120;320\right)=\left\{40;80;120;160;200;...\right\}\)
\(ƯCLN\left(120;320\right)=2^3.5=40\)
\(b.455=5.7.13\)
\(950=2.5^2.19\)
\(ƯC\left(455;950\right)=\left\{5;10;15;20;25;...\right\}\)
\(ƯCLN\left(455;950\right)=5\)
\(c.126=2.3^2.7\)
\(108=2^2.3^3\)
\(306=2.3^2.17\)
\(ƯC\left(126;108;306\right)=\left\{18;36;54;72;...\right\}\)
\(ƯCLN\left(126;108;306\right)=2.3^2=18\)
a.120=23.3.5�.120=23.3.5
320=26.5320=26.5
ƯC(120;320)={40;80;120;160;200;...}Ư�(120;320)={40;80;120;160;200;...}
ƯCLN(120;320)=23.5=40Ư���(120;320)=23.5=40
b.455=5.7.13�.455=5.7.13
950=2.52.19950=2.52.19
ƯC(455;950)={5;10;15;20;25;...}Ư�(455;950)={5;10;15;20;25;...}
ƯCLN(455;950)=5Ư���(455;950)=5
c.126=2.32.7�.126=2.32.7
108=22.33108=22.33
306=2.32.17306=2.32.17
ƯC(126;108;306)={18;36;54;72;...}Ư�(126;108;306)={18;36;54;72;...}
ƯCLN(126;108;306)=2.32=18
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\(2^{30}< 2^{300}< 3^{200}\)
\(\Rightarrow2^{30}< 3^{200}\)
\(3^{200}=\left(3^2\right)^{100}=9^{100}=9^{30}\cdot9^{70}\)
Vì \(9>2\) nên \(9^{30}>2^{30}\) hay \(9^{30}\cdot9^{70}>2^{30}\)
Từ đó \(9^{100}>2^{30}\) hay \(2^{30}< 3^{200}\)
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Bài làm
122 . 127 + 123 - 144 . 27
= 144 . 127 + 123 - 144 . 27
= 144 . ( 127 - 27 ) + 144
= 144 . 100 + 144
= 14400 + 144
= 14544
# Chúc bạn học tốt #
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16 : { 780 : [500-(53+35.7)+1000+42.4]}
= 16 : { 780 : [ 500-(125+245)+1+43 ]}
= 16 : { 780 : [ 500-370+1+64]}
= 16 : ( 780 : 195)
= 16 : 4
= 4
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a: \(\Leftrightarrow5x-42=251\)
=>5x=293
hay x=293/5
b: \(\Leftrightarrow20-x=20\)
hay x=0
c: \(\Leftrightarrow x-4300-\dfrac{1}{50}=4250\)
\(\Leftrightarrow x=\dfrac{427501}{50}\)
d: =>(x+200):4=460-340=120
=>x+200=480
hay x=280
e: =>5+15(x+1)=500-480=20
=>15(x+1)=15
=>x+1=1
hay x=0