( 17 / 31 trừ 7/62 ) nhân -31/54
17/31 - 7/62 * - 31 / 54
tính nhanh
131 nhân 27 trừ 31 nhân 27 trừ 7 nhân 100
131 . 27 - 31 . 27 - 7.100
b1 :
5 , 31 + 62 x 20 + 31 x 59
6, -19 + 38 x 22 + 31 x 59
7, 54 ( -11 - 32 ) - 32 (89 - 54 )
8,2018 x 31 - 2018 ( -19 ) + 2018 x 50
9, 16 x 34 - (-16 ) x 21 + 55 x 16
10 , 29 x 63 - 63 x 31 - 63 x 98
ai làm hết mkcho 10 tick trong 1 buổi tối
5, 31+1240++1829=3100
6. -19+836+1829=2646
7. 54.43-32.35=2322-1120=1202
8 2018(31+16+50)=2018.97=195746
9. 16(34-21+55)=16.68=1088
10. 63(29-31-98)=63.(-100)=-6300
31 nhân 15 nhân 7mũ2 nhân 4 trừ 31 nhân 49 nhân 40
Bài1: Thực hiện phép tính sau:
a:2/7-1/5.10/7
b:19/23+1/9.36/23
c:(17/31-7/62).-31/54
d:(3/7+4/3). (5/37-2/37)
Bài:2 Tính
A=3/2.5+3/5.8+...+3/17.20
B=5^2/1.6+5^2/6.11+5^2/11.16+...5^2/26.31
Giúp mình với mình đang cần gấp .......
Bài 2:
\(A=\dfrac{3}{2\cdot5}+\dfrac{3}{5\cdot8}+...+\dfrac{3}{17\cdot20}\)
\(=\dfrac{1}{2}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{8}+...+\dfrac{1}{17}-\dfrac{1}{20}\)
\(=\dfrac{1}{2}-\dfrac{1}{20}=\dfrac{9}{20}\)
\(B=\dfrac{5^2}{1\cdot6}+\dfrac{5^2}{6\cdot11}+...+\dfrac{5^2}{26\cdot31}\)
\(=5\left(\dfrac{5}{1\cdot6}+\dfrac{5}{6\cdot11}+...+\dfrac{5}{26\cdot31}\right)\)
\(=5\left(1-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{11}+...+\dfrac{1}{26}-\dfrac{1}{31}\right)\)
\(=5\left(1-\dfrac{1}{31}\right)=5\cdot\dfrac{30}{31}=\dfrac{150}{31}\)
a) Chứng minh: B = 31 + 32 + 33 + 34 + … + 32010 chia hết cho 4.
b) Chứng minh: C = 51 + 52 + 53 + 54 + … + 52010 chia hết cho 31.
c) Cho S=17+52+53+54+ ... +52010 . Tìm số dư khi chia S cho 31.
\(B=3+3^2+3^3+3^4+...+3^{2009}+3^{2010}\)
\(=\left(3+3^2\right)+\left(3^3+3^4\right)+...+\left(3^{2009}+3^{2010}\right)\)
\(=3\left(1+3\right)+3^3\left(1+3\right)+...+3^{2009}\left(1+3\right)\)
\(=4.\left(3+3^3+...+3^{2009}\right)\)
⇒ \(B\) ⋮ 4
b: \(C=5\left(1+5+5^2\right)+...+5^{2008}\left(1+5+5^2\right)=31\cdot\left(5+...+5^{2008}\right)⋮31\)
x+(-45)=(-62)+17
(689-31)-(269-111)
x+(-45)=(-62)+17
x+(-45)=-45
x =-45+45
x =0
(689-31)-(269-111)
=689-31-269+111
=(689+111)-(31+269)
= 800 - 300
= 500
1) x + ( -45 ) = -45
x = -45 - ( -45)
x= 0
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=?