a) -(415) + (-210) -367 + 62
b) -69./-45/ -31./45/
c) 3.(-4) +2.(-50)-12
1tính
a) (-6-18 ) : (-4)
b) -28 . (50-42 ) - 35 . ( 34 - 62 )
c) -18 - (-5) + 26
d) -72 . 69 + 31 . (-72)
e) 7 . (-6)2 + ( -42) .17
f) (-38+45 ). ( -36)
2 tìm x
a) x + 49 = 17
b) 18-3x=-15
c) (x-5)=2
d) 15-3(x-2)=-6
e) 36-(18+x)=55
f) -4 |x|=-12
a)(-6-18):(-4)
= { (-6) + (-8) } : (-4)
=(-24) : (-4)= (-6)
b)-28.(50-42)-35.(34-62)
= -28.8-35.(-28)
= -28.(8-35)
= -28.(-27)=756
c)-18-(-5)+26
= -18+5+26
= -13+26=13
d)-72.69+31.(-72)
= -72.(69+31)
= -72.100=-7200
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40+41+42+43+44+45+46+47+48+49+50+51+52+53+54+56+57+58+59+60+61+62+63+64+65+66+67+68+69+70=?
bài 2: thực hiện phép tính bằng cách hợp lý(nếu có thể)
a)(-31)+(50-19)-(150-31)
b)25.(45-17)-45.(25-17)
c)-1/12 + 4/3
d)3/5 + -5/20+ 30/75 + -7/4
\(a)\)
\(\left(-31\right)+\left(50-19\right)-\left(150-31\right)\)
\(=\left(-31\right)+50-19-150+31\)
\(=\left(-150\right)-19\)
\(=-169\)
\(b)\)
\(25.\left(45-17\right)-45.\left(25-17\right)\)
\(=25.45-25.17-45.25+45.17\)
\(=0\)
\(c)\)
\(\frac{-1}{12}+\frac{4}{3}=\frac{5}{4}\)
\(d)\)
\(3+\frac{-5}{20}+\frac{30}{75}+\frac{-7}{4}\)
\(=\left(\frac{3}{5}+\frac{30}{75}\right)-\left(\frac{5}{20}+\frac{7}{4}\right)\)
\(=1-2\)
\(=-1\)
a) (-31)+(50-19)-(150-31)
= (-31)+50+(-19)-150+(-31)
= (-31)+50-150+(-19)-(-31)
= (-31)+(-100)+12
= -119
b) 25(45-17)-45(25-17)
= 25.45-25.17-45.25-45.17
= 25(45-45)-25(17-17)
= 0
c) -1/12 + 4/3
= -1/12 + 16/12
= 15/12
= 5/4
d) 3/5+(-5)/20+30/75+(-7)/4
= 45/75+30/75+(-5)/20+(-35)/20
= 1+(-2)
= -1
Bài 6: Thực hiện phép tính
a)(-18)-(-3)-12
b)85.(35-27)-35.(85-27)
c)(-45).69+31.(-45)
Bài 7:Tìm x thuộc Z, biết:
a)(2-x)+10=-14
b)14.|x|=28
c)31-(17+x)=55
Bài 6:
a)\(\left(-18\right)-\left(-3\right)-12\)
\(=\left(-18\right)+3-12\)
\(=-15-12\)
\(=-27\)
b)\(85.\left(35-27\right)-35.\left(85-27\right)\)
\(=85.35-85.27-35.85+35.27\)
\(=85.\left(35-27-35\right)+35.27\)
\(=85.\left(-27\right)+35.27\)
\(=27.\left(-85+35\right)\)
\(=27.\left(-50\right)\)
\(=-1350\)
c)\(\left(-45\right).69+31.\left(-45\right)\)
\(=\left(-45\right).\left(69+31\right)\)
\(=\left(-45\right).100\)
\(=-4500\)
Bài 7:
a)\(\left(2-x\right)+10=-14\)
\(\Rightarrow2-x=-24\)
\(\Rightarrow x=26\)
b)\(14.\left|x\right|=28\)
\(\Rightarrow\left|x\right|=2\)
\(\Rightarrow\orbr{\begin{cases}x=2\\x=-2\end{cases}}\)
c)\(31-\left(17+x\right)=55\)
\(\Rightarrow17+x=-24\)
\(\Rightarrow x=-41\)
(-18)-(-3)-12=-27
85.(35-27)-35.(85-27)=-1350
(-45).69+31.(-45)=-4500
(2-x)+10=-14
\(\Leftrightarrow\)(2-x)=-14-10
\(\Leftrightarrow\)2-x=-24
\(\Rightarrow\)x=2-(-24)
\(\Rightarrow\)x=26
14.lxl=28
\(\Leftrightarrow\)lxl=28:14
\(\Leftrightarrow\)lxl=2
\(\Rightarrow\)x=-2
a, 26,72 + 13/100 + 21/40
b, 1/4 + 17/50 + 31/100
c, 3/4 + 15/40 + 69/300
d, 42/700 + 45/120 + 17/80
ai rảnh thì làm nha
mình có ý kiến ?
1.Tính hợp lý
a)(-53):101
b)(-45)(-16)(-125).(-4)^10
c)12+(-47).12-69-12)
d)32(132-247)-132(31-247)
Bài 6: Thực hiện phép tính
a)(-18)-(-3)-12
b)85.(35-27)-35.(85-27)
c)(-45).69+31.(-45)
Bài 7:Tìm x thuộc Z, biết:
a)(2-x)+10=-14
b)14.|x|=28
c)31-(17+x)=55
Bài 6: Thực hiện phép tính
a)(-18)-(-3)-12
= (-18) + 3 - 12
= (-15) - 12
= - 3
b)85.(35-27)-35.(85-27)
= 85. 8 - 35. 58
= 680. 2030
= 1380400
c)(-45).69+31.(-45)
= (-45) . (69 + 31)
= (-45) . 100
= - 4500
Bài 7:Tìm x thuộc Z, biết:
a)(2-x)+10=-14
2-x = 14 - 10
2-x = 4
x = 2 - 4
x = - 2
b)14.|x|=28
|x| = 28 : 14
|x| = 2
⇒ x ϵ {2;-2}
Tính hợp lí (nếu có thể):
a) 2 . 31 . 12 + 4 . 6 . 42 + 8 . 27 . 3
b) (39 . 9 + 39 . 12) : 310
c) 36 . 28 + 36 . 82 + 64 . 69 + 64 . 41
d) [545 - (45 + 4 . 25)] : 50 - 2000 : 250 + 215 : 213
e) [504 - (25 . 8 + 70)] : 9 - 15 + 190
f) 5 . {26 - [3 . (5 + 2 . 5) + 15] : 15}
a)0,75 + 15/6 : 5 - 1/36 . (-3)2 + (-2020/2021)
b)45. 94 - 2 . 69/210 . 38 + 68 . 20
b: \(\dfrac{4^5\cdot9^4-2\cdot6^9}{2^{10}\cdot3^8+6^8\cdot20}\)
\(=\dfrac{2^{10}\cdot3^8-2^{10}\cdot3^9}{2^{10}\cdot3^8+3^8\cdot2^{10}\cdot5}\)
\(=\dfrac{2^{10}\cdot3^8\left(1-3\right)}{2^{11}\cdot3^9}\)
\(=\dfrac{1}{2}\cdot\dfrac{-2}{3}=\dfrac{-1}{3}\)
Sửa đề câu a) phải là (-2020/2021)0
Xin lỗi mn
\(a,=\dfrac{3}{4}+\dfrac{15}{6}\cdot\dfrac{1}{5}-\dfrac{1}{36}\cdot9-\dfrac{2020}{2021}=\dfrac{3}{4}+\dfrac{1}{2}-\dfrac{1}{4}-\dfrac{2020}{2021}=1-\dfrac{2020}{2021}=\dfrac{1}{2021}\\ b,=\dfrac{2^{10}\cdot3^8-2\cdot2^9\cdot3^9}{2^{10}\cdot3^8+2^8\cdot3^8\cdot2\cdot5}=\dfrac{2^{10}\cdot3^8\left(1-3\right)}{2^9\cdot3^8\left(2+5\right)}=\dfrac{2\left(-2\right)}{3}=-\dfrac{4}{3}\)