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1.
a) \(125+80+375+220\)
\(=\left(125+375\right)+\left(80+220\right)\)
\(=500+300\)
\(=800\)
b) \(25.11.8.4.125\)
\(=\left(25.4\right).\left(8.125\right).11\)
\(=100.1000.11\)
\(=1100000\)
c) \(18.74+18.27-18\)
\(=18.\left(74+27-1\right)\)
\(=18.100\)
\(=1800\)
d) \(75.23+75.77-500\)
\(=75.\left(23+77\right)-500\)
\(=75.100-500\)
\(=7500-500\)
\(=7000\)
e) \(150:\left[25.\left(18-4^2\right)\right]\)
\(=150:\left[25.\left(18-16\right)\right]\)
\(=150:\left[25.2\right]\)
\(=150:50\)
\(=3\)
f) \(125.23.2.8.50\)
\(=\left(125.8\right).\left(2.50\right).23\)
\(=1000.100.23\)
\(=2300000\)
g) \(235+88+165+12\)
\(=\left(235+165\right)+\left(88+12\right)\)
\(=400+100\)
\(=500\)
h) \(71.32+71.68-1100\)
\(=71.\left(32+68\right)-1100\)
\(=71.100-1100\)
\(=7100-1100\)
\(=6000\)
i) \(6^7:6^6+4^3.2-24^0\)
\(=6+64.2-1\)
\(=6+128-1\)
\(=133\)
j) \(546-6.\left[158:\left(30+7^2\right)\right]\)
\(=546-6.\left[158:\left(30+49\right)\right]\)
\(=546-6.\left[158:79\right]\)
\(=546-6.2\)
\(=546-12\)
\(=534\)
k) \(268+147+132+253\)
\(=\left(268+132\right)+\left(147+253\right)\)
\(=400+400\)
\(=800\)
2.
a) \(7x=707\)
\(x=707:7\)
\(x=101\)
b) \(6x+5=47\)
\(6x=47-5\)
\(6x=42\)
\(x=42:6\)
\(x=7\)
c) \(35:\left(x+1\right)=7\)
\(x+1=35:7\)
\(x+1=5\)
\(x=5-1\)
\(x=4\)
d) \(12+\left(29-3x\right)=35\)
\(29-3x=35-12\)
\(29-3x=23\)
\(3x=29-23\)
\(3x=6\)
\(x=6:3\)
\(x=2\)
e) \(2.4^x+10^1=138\)
\(2.4^x=138-10\)
\(2.4^x=128\)
\(4^x=128:2\)
\(4^x=64=4^3\)
\(\Rightarrow x=3\)
f) \(7x=140\)
\(x=140:7\)
\(x=20\)
g) \(7\left(15-x\right)+14=84\)
\(7\left(15-x\right)=84-14\)
\(7\left(15-x\right)=70\)
\(15-x=70:7\)
\(15-x=10\)
\(x=15-10\)
\(x=5\)
h) \(3^x.5-15=390\)
\(3^x.5=390+15\)
\(3^x.5=405\)
\(3^x=405:5\)
\(3^x=81=3^4\)
\(\Rightarrow x=4\)
1/\(\left(-12\right)\cdot46-12\cdot54=\left(-12\right)\cdot46+\left(-12\right)\cdot54\)
\(=\left(-12\right)\cdot\left(46+54\right)=\left(-12\right)\cdot100=-1200\)
2/\(3784+23-3785-15=3785+22-3785-15\)
\(=22-15=7\)
3/\(\left(-8\right)\cdot25\cdot\left(-2\right)\cdot4\cdot\left(-5\right)\cdot125\)
\(=\left[\left(-8\right)\cdot125\right]\cdot\left[25\cdot4\right]\cdot\left[\left(-5\right)\cdot\left(-2\right)\right]\)
\(=\left(-1000\right)\cdot100\cdot10=-1000000\)
4/\(19\cdot25+9\cdot95+19\cdot30=19\cdot\left(25+30\right)+9\cdot95\)
\(=19\cdot55+9\cdot95=95\cdot11+9\cdot95=95\cdot\left(11+9\right)=20\cdot95=1900\)
5/\(\left(-50+19+143\right)-\left(-79+25+48\right)\)
\(=\left(-50\right)+19+143+79-25-48\)
\(=118\)
6/\(\left(-25\right)\cdot\left(75-45\right)-75\cdot\left(45-25\right)\)
\(=\left(-25\right)\cdot30+\left(-25\right)\cdot3\cdot20\)
\(=\left(-25\right)\cdot\left(30+60\right)=\left(-25\right)\cdot90=-2250\)
7/\(\left(-37-17\right)\cdot\left(-9\right)+35\left(-9-11\right)\)
\(=\left(-54\right)\cdot\left(-9\right)+35\cdot\left(-20\right)\)
\(=486+\left(-700\right)=-214\)
8/\(\left(187-23\right)-\left(20-180\right)\)
\(=187-23-20+180=324\)
9/\(512\cdot2-128\cdot\left(-512\right)\)
\(=512\cdot2+128\cdot512=512\cdot\left(2+128\right)\)
\(=512\cdot130=66560\)
10/\(17\cdot\left(-25\right)+25\cdot21\)
\(=17\cdot\left(-25\right)-\left(-25\right)\cdot21=\left(-25\right)\cdot\left(17-21\right)\)
\(=\left(-25\right)\cdot\left(-4\right)=100\)
Chúc bạn học tốt.
1) (-12).46-12.54
=12.(-46)-12.54
=12.(-46-54)
=12.(-100)=(-1200)
10) 17.(-25)+25.21
= (-17).25+25.21
=25.(-17+21)
=25.4=100
( Mik đọc lướt qua thì thấy hai bài này dễ nên làm, chứ mấy bài kia chưa suy nghĩ gì, bạn tự làm nốt nhé!)
1) 125.(-24) + 24.225.
\(=24\left(-125+225\right)=24.100=2400.\)
2) 512.(2 – 128) – 128. (-512).
\(=512\left(2-128+128\right)=512.2=1024.\)
a,=23(-75-25)-15.8
=23.(-100)-120
=-100.(23+12)
=-100.45=-4500
b,=150-(300+540+130)
=150-960=-810
a) - 23 . 75 - 25 . 23 - 15 . 23
= - 23 . 75 - 25 . 23 - 15 . 8
=-2420
b) 150 - ( 150 . 2 + 180 . 3 + 180 . 2 : 3 )
= 150 - ( 300 + 540 + 120 )
= 150 - 300 - 540 - 120
=-810