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7: =-1+8=7
6: \(=-\left(8\cdot125\right)\cdot\left(2\cdot5\right)\cdot\left(25\cdot4\right)=-1000000\)
5: =-50+19+143+79-25-48
=-75+98+95
=23+95
=118
4: =37x9+17x9-35x9-35x11
=18+153-385
=-214
3: =187-23-20+180
=367-43
=324
4: \(=37\cdot9+17\cdot9-35\cdot9-35\cdot11=19\cdot9-385\)
\(=171-385=-214\)
5: =-50+19+143+79-25-48
=-75+94+95
=20+94
=114
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) 27 + 55 + (-17) + (-55) = (27 - 17) + (55 - 55) = 10
b) (-92) + (-251) + (-8) + 251 = (-92 - 8) + (-251 + 251) = -100
c) (-31) + (-95) + 131 + (-5) = (-31 + 131) + (-95 - 5) = 100 - 100 = 0
d) S1 = 2 - 4 + 6 - 8 + ... + 1998 - 2000 = (2 - 4) + (6 - 8) + ... + (1998 - 2000) (gồm 500 cặp) = -2 - 2 - ... - 2 = -2 . 500 = -1000
S2 = 2 - 4 - 6 + 8 + 10 - 12 - 14 + 16 + ... + 1994 - 1996 - 1998 + 2000
= (2 - 4 - 6 + 8) + (10 - 12 - 14 + 16) + .... + (1994 - 1996 - 1998 + 2000)
= 0 + 0 + ... + 0 = 0
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.