1, B = 55 . 5 + 20140
2,
a. x + 180 : 18 = 30
b. (x+ 180) : 18 = 30
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180 : ( 18 x 5 )
= 180 : 90
= 2
b) 240 : ( 2 x 3 x 4 )
= 240 : 24
= 10
c) 4400 : ( 22 x 35 )
= 4400 : 770
= \(\dfrac{40}{7}\)
a: \(42=2\cdot3\cdot7;70=2\cdot5\cdot7\)
=>\(BCNN\left(42;70\right)=2\cdot3\cdot5\cdot7=210\)
=>\(BC\left(42;70\right)=B\left(210\right)=\left\{0;210;420;...\right\}\)
b: \(70=2\cdot5\cdot7;180=3^2\cdot5\cdot2^2\)
=>\(BCNN\left(70;180\right)=2^2\cdot3^2\cdot5\cdot7=1260\)
=>\(BC\left(70;180\right)=\left\{1260;2520;...\right\}\)
c: \(5=5;7=7;8=2^3\)
=>\(BCNN\left(5;7;8\right)=5\cdot7\cdot8=280\)
=>\(BC\left(5;7;8\right)=\left\{280;560;...\right\}\)
d: \(12=2^2\cdot3;18=3^2\cdot2\)
=>\(BCNN\left(12;18\right)=2^2\cdot3^2=36\)
=>\(BC\left(12;18\right)=\left\{36;72;...\right\}\)
e: \(15=3\cdot5;18=3^2\cdot2\)
=>\(BCNN\left(15;18\right)=3^2\cdot2\cdot5=90\)
=>\(BC\left(15;18\right)=\left\{90;180;...\right\}\)
f: \(84=2^2\cdot3\cdot7;108=3^3\cdot2^2\)
=>\(BCNN\left(84;108\right)=2^2\cdot3^3\cdot7=756\)
=>\(BC\left(84;108\right)=\left\{756;1512;...\right\}\)
j: \(33=3\cdot11;44=2^2\cdot11;55=5\cdot11\)
=>\(BCNN\left(33;44;55\right)=3\cdot2^2\cdot5\cdot11=660\)
=>\(BC\left(33;44;55\right)=\left\{660;1320;...\right\}\)
g: \(1=1;12=2^2\cdot3;27=3^3\)
=>\(BCNN\left(1;12;27\right)=1\cdot2^2\cdot3^3=108\)
=>\(BC\left(1;12;27\right)=\left\{108;216;...\right\}\)
n: \(5=5;9=3^2;11=11\)
=>\(BCNN\left(5;9;11\right)=5\cdot3^2\cdot11=495\)
=>\(BC\left(5;9;11\right)=\left\{495;990;...\right\}\)
(\(x\) + 2) + (\(x\) + 4) +...+ (\(x\) + 18) = 180
xét dãy số: 2; 4; ...;18
Dãy số trên là dãy số cách đều với khoảng cách là: 4-2 = 2
Số số hạng của dãy số trên là: (18 - 2) : 2 + 1 = 9
Vậy ta có:
9\(x\) + ( 18 + 2) \(\times\) 9: 2 = 180
9\(x\) + 90 = 180
9\(x\) = 90
\(x\) = 10
1)tính
a)\(-17+\left(-19\right)+25\)
\(=-17-19+25\)
\(=-\left(17+19\right)+25\)
\(=-36+25\)
\(=-\left(36-25\right)\)
\(=-11\)
b)\(-26+\left(-25\right)-18\)
\(=-26-25-18\)
\(=-\left(26+25\right)-18\)
\(=-51-18\)
\(=-\left(51+18\right)\)
\(=-69\)
c)\(35-\left(-19\right)-19-8\)
\(=35+19-19-8\)
\(=35+\left(19-19\right)-8\)
\(=35+0-8\)
\(=35-8\)
\(=27\)
d)\(1963-\left(-180\right)-1990\)
\(=1963+180-1990\)
\(=2143-1990\)
\(=153\)
2)Tìm x thuộc z biết
a)\(x-\left(-18\right)=25+\left(-17\right)\)
\(\Leftrightarrow x+18=25-17\)
\(\Leftrightarrow x+18=8\)
\(\Leftrightarrow x=8-18\)
\(\Leftrightarrow x=-10\)
Vậy x=-10
b)\(x-28=-27-30\)
\(\Leftrightarrow x-28=-\left(27+30\right)\)
\(\Leftrightarrow x-28=-57\)
\(\Leftrightarrow x=-57+28\)
\(\Leftrightarrow x=-\left(57-28\right)\)
\(\Leftrightarrow x=-29\)
Vậy x=-29
c)\(35-\left(-x\right)=27-18-\left(-8\right)\)
\(\Leftrightarrow35+x=27-18+8\)
\(\Leftrightarrow35+x=9+8\)
\(\Leftrightarrow35+x=17\)
\(\Leftrightarrow x=17-35\)
\(\Leftrightarrow x=-18\)
Vậy x=-18
d)\(40+\left(-x\right)=35-\left(-27\right)\)
\(\Leftrightarrow40-x=35+27\)
\(\Leftrightarrow40-x=62\)
\(\Leftrightarrow x=40-62\)
\(\Leftrightarrow x=-22\)
Vậy x=-22
1.
B=5^5 x 5 + 20140
B= 3125 x 5 + 0
B=15625+0
=>B=15625
2.
a) x + 180 :18=30
x + 10 =30
=>x=30-10
x=20
b) (x + 180):18=30
x +180 =30 x 18
x +180 = 540
x =540 -180
==>x = 360