a) 22 + 23 + 24 + ... + 2119
Đặt A=22 + 23 + ... + 2119
2A=2(22 + 23 + ... + 2119)
2A=23+24+...+2120
2A-A=(23+24+...+2120)-(22 + 23 + ... + 2119)
A=2120-22
b)Đặt B= 2 + 22 + 23 + 24 + ... + 2101
2B=2( 2 + 22 + 23 + 24 + ... + 2101)
2B=22+23+...+2102
2B-B=(22+23+...+2102)-( 2 + 22 + 23 + 24 + ... + 2101)
B=2102-2
S=5/20+5/21+5/22+5/23+5/24
S = 5/20 + 5/21 + 5/22 + 5/23 + 5/24
tính giá trị biểu thức và chứng minh S > 1
Tính nhanh :
1 + 7 + 8 + 15 + 23 + ... + 160
1 + 4 + 5 + 9 + 14 + ... + 60 + 97
78 x 31 + 78 x 24 + 78 x 17 + 72 x 22
A = 1 x 4 + 2 x 5 + 3 x 6 + 4 x 7 + .... n x ( n+ 3 )
Giúp mình nha,ai làm chi tiết và đúng mình tích 15 cái
1. Tính
a, 1+7+8+15+23+...+160
b, 17+4+5+9+19+...+60+9
c, 78*3+78*24+78*17*22*72
d, 53*39+47*39+47-53*21-47*21
e, 2*53*12+4*6*87-3*8*40
g, 5*7*77-7*60+49*25-15*42
h, 1*2+2*3+3*4+...+2016*2017
A=1/2+1/22+1/23+...1/2100 chứng tỏ0<A<1
A=1/21+1/22+1/23+1/24+...1/40 chứng tỏ1/2<A<1
khó wá
tính hợp lí nhất :
1, 35 . ( 14 - 23 ) - 23 . ( 14 - 35 )
2 , 27 . ( 13 - 16 ) - 16 .( 13 - 27 )
3, 44 . (-36 ) + 22 . ( - 28 )
Mình sẽ mở một cuộc thi Toán 6 bạn nào muốn tham gia thì giải bài dưới đây nếu đạt mình sẽ mở vòng 2 ^^
ĐỀ CƯƠNG ÔN TẬP TOÁN 6
Bài 1 : Thực hiện phép tính :
a. 17.85 + 15.17 - 120 b.5.72 - 24:23 c. 33. 22 - 27.19 d. -|-3| + ( - 23 ) e. -|-13| + |-25 | + | 12 |
f. 23 - ( 12 - 42 ) g. 80 - [ 130 - ( 12 - 4 )2 ] h. 24.5 [ 131 - ( 13 - 22 ]2 ] i. - ( -23 ) + | - 13 | - | - 42 |
k. ( 315.4 + 5.315 ) : 316 l. 1125 : 32 + 43.125 - 125 : 52 m. |-18 | : | -6 | - ( -12 ) + ( -20 )
BÀI LÀM
a.________________________________________b.________________________________c._________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Bài 1: Tính :
5) 23 - { 4 . 24 - [ 2\(^5\) . 3\(^2\) - ( 180 : 3\(^2\) ) ] }
Bài 2: Tìm x biết:
1) x + 23 = -11
2) x - 24 = -11
tính nhanh
20+21+22+23+...+29+30
