Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
a ) 128 . ( 278 - 302 ) + 278 . ( 302 - 128 )
= 128 . 278 - 128 . 302 + 278 . 302 - 128 . 278
= ( 128 . 278 - 128 . 278 ) + ( 278 . 302 - 128 . 302 )
= 302 . ( 278 - 128 )
= 302 . 100 = 30200 .
b ) 2 . ( - 7 )2 - 3 . ( - 4 )3 - 60
= 2 . 49 + 192 - 60
= 98 + 192 - 60
= 230 .
YẾN ƠI TUI BẠN BÀ NÈ
NHƯNG TUI HỔNG PHẢI LỚP 6 THÔNG CẢM NHA
a)\(\left(10^2+11^2+12^2\right)\div\left(13^2+14^2\right)\)
\(=\left(100+121+144\right)\div\left(169+196\right)\)
\(=365\div365\)
\(=1\)
b) \(1.2.3...9-1.2.3...8-1.2.3...8^2\)
\(=1.2.3...8\left(9-1-8\right)\)
\(=1.2.3...8.0\)
\(=0\)
d) \(1152-\left(374+1152\right)+\left(-65+374\right)\)
\(=1152-374-1152-65+374\)
\(=\left(1152-1152\right)-65+\left(374-374\right)\)
\(=0-65+0\)
\(=-65\)
e) \(13-12+11+10-9+8-7-6+5-4+3+2-1\)
\(=13-\left(12-11\right)+\left(10-9\right)+\left(8-7\right)-\left(6-5\right)-\left(4-3\right)\)\(+\left(2-1\right)\)
\(=13-1+1+1-1-1+1\)
\(=13+0+0+0\)
\(=13\)
a)(-37)+54+(-70)+(-163)+246=[(-37)+(-163)]+(54+246)+(-70)=(-200)+300+(-70)=100+(-70)=30
b)1152-(374+1152)+(-65+374)=1152-374-1152+(-65)+374=[(-374)+374]+(1152-1152)+(-65)=0+0+(-65)=-65
c ) S = 1.2 + 2.3 + 3.4 + .... + 99.100
=> 3S = 1.2.3 + 2.3.3 + 3.4.3 + .... + 99.100.3
=> 3S = 1.2.3 + 2.3.( 4 - 1 ) + 3.4.( 5 - 2 ) + .... + 99.100.( 101 - 98 )
=> 3S = 1.2.3 + 2.3.4 - 1.2.3 + 3.4.5 - 2.3.4 + .... + 99.100.101 - 98.99.100
=> 3S = ( 1.2.3 - 1.2.3 ) + ( 2.3.4 - 2.3.4 ) + .... + ( 98.99.100 - 98.99.100 ) + 99.100.101
=> 3S = 99.100.101 => S = \(\frac{99.100.101}{3}\)
d ) Ta có \(\frac{1}{2^2}<\frac{1}{2.1}=\frac{1}{1}-\frac{1}{2}\)
\(\frac{1}{3^2}<\frac{1}{2.3}=\frac{1}{2}-\frac{1}{3}\)
..........
\(\frac{1}{100^2}<\frac{1}{99.100}=\frac{1}{99}-\frac{1}{100}\)
Vậy \(\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+....+\frac{1}{100^2}<\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+....+\frac{1}{99}-\frac{1}{100}\)
\(\Leftrightarrow\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+....+\frac{1}{100^2}<\frac{1}{1}-\frac{1}{100}=\frac{99}{100}<1\)
Bài 1:
A,
(100+121+144)÷(169+196)
=365:365=1
B
,1.2.3...7.8.(9-1-8)
=1.2.3...7.8.0=0
C,
3^2.2^4.2^32/11.2^13.2^22-2^26
=3^2.2^36/11.2^35-2^36
=3^2.2^36/2^35-(11-2)
=9.2/9=2
D,
=1152-374-1152+(-65)+374
=(1152-1152)+(-374+374)+(-65)
=0+0+(-65)=-65
E,
=13-(12-11-10+9)+(8-7-6+5)-(4-3-2+1)
=13-0+0-0=13
Bài 2:
A,(19x+50)÷14=25-16
(19x+50)÷14=9
19x+50=126
19x=76
x=4
B,
31x+(1+2+3+...+30)=1240
31x+465=1240
31x=775
×=25
Bài 1:
a) \(128\cdot\left(278-302\right)+278\cdot\left(302-142\right)\)
\(=128\cdot278-128\cdot302+278\cdot302-278\cdot142\)
\(=41408\)
b) \(\left(-2\right)\cdot\left(-6\right)^2+3\cdot\left(-2\right)^3-62\)
\(=\left(-2\right)-36-24-62=-2-36-24-62=-124\)
c) \(1152-\left(374+1152\right)+\left(-65+374\right)\)
\(=1152-374-1152-65+374=-65\)
d) \(-215\cdot54-430\cdot23=-215\cdot54-215\cdot46=-215\left(54+46\right)=-215\cdot100=-21500\)
e) \(\left(-2\right)+\left(-49\right)+\left(-18\right)+49=-20\)
a/128.(278-302)+278.(302-142)
=128(-24)+278.160
=-3072+44480
=41408
b/(-2).(-6)2+3.(-2)3-62
=-2.(-36)+3.(-8)-62
=72+(-24)-62
=48-62
=-14