1^3+2^3+3^3=36
bạn michelle Trần SAi rồi
13 + 23 + 33 = 1 + 8 + 27 = 36 hộ
nhớ ủng hộ mmik nha mn
Chứng minh rằng:
a,A=1/2+1/2^2+1/2^3+.+1/2^2<1
b,B=1/3+1/3^2+1/3^3+...+1/3^n<1/2
c,B=1/2-1/2^2+1/2^3-1/2^4+...+1/2^2015-1/2^2016<1/3
d,D=1/3+2/3^2+3/3^3+4/3^4+...+100/3^100<3/4
bài 3:
a) x - 3/4 = 6 x 3/8 b) 7/8 : x = 3 - 1/2 c) x + 1/2 x 1/3 = 3/4
d) 3/2 x 4/5 - x = 2/3 e) X x 3 1/3 = 3 1/3 : 4 1/4 f) 5 2/3 : x = 3 2/3 - 2 1/2
a,1/3 .(x-2/5)=3/4 b, 7/3:(x-2/3)=4/5 c,1/3.(x-2/5)=4/5 d, 2/3.(x-1/2)-1/4.(x-2/5)=7/3 e,3/7 .(x-2/3)+1/2=5/4.(x-2) f,1/2.(x-3)+1/3.(x-4)+1/4.(x-5)=1/5 g,[2/3.(x-1/2)-4/5]:(x-1/3)=21/5 h, {x-[1/2.(x-3)+11/5]}:(x-1/2)=3/5 i,x.(x-2/5)-(x+2).x+11/4=4/3
1^3 + 2^3
1^3 + 2^3 + 3^3
1^3 + 2^3 + 3^3 + 4^3
3/1+2+3/1+2+3+3+1+2+3+4+........+3/1+2+3+......+20
3/1+2+3/1+2+3+3/1+2+3+4+......+3/1+2+3+...+20
Tính A=3+3/1+2+3/1+2+3+3/1+2+3+4+..+3/1+2+3+4+......+100
(3/1+2)+(3/1+2+3)+(3/1+2+3+4)+...+(3/1+2+3+..+50)-0.5X=1/100
3\1+2+3\1+2+3+3\1+2+3+4+3\1+2+3+...+50-0.5x=1\100
B=3^100-3^99-3^98-..-3-1
B=3^100-(3^99+3^98+...+3+1)
ta có:M=3^99+3^98+..+3+1
3M=3^100+3^98+...+3^2+3
2M=3M-M=3^100+3^99+3^98+...+3^2+3-3^99+3^98+...+1
2M=3^100-1
=>B=3^100-3^100+1:2
B=0+1/2
B=1/2
