Gọi tổng trên là A.Ta có:
A=1/1x3+1/3x5+1/5x7+1/7x9+1/9x11
2A=2/1x3+2/3x5+2/5x7+2/7x9+2/9x11
2A=1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11
2A=1-1/11
2A=11/11-1/11
2A=10/11
A=10/11:2
A=5/11
1/1×3+1/3×5+1/5×7+1/7×9+1/9×11
Tính
a) 4/3*7 + 4/7*11 + 4/11*15 + 4/15*19 + 4/19*23 + 4/23*27
b) 1/2*3 + 1/3*4 + 1/4*5 + 1/5*6 +1/6*7
c) 2/3*5 + 2/5*7 + 2/7*9 + 2/9*11 + 2/11*13 + 2/1*2 + 2/2*3 + 2/3*4 + 2/8*9 + 2/9*10
a/2-3+5-7+9-11+13-15+17
b/1/1×2+1/2×3+1/3×4+1/4×5+1/5×6+1/6×7+1/7+8+1/8×9
5/6 + 7/8
2+2/3
7/9 - 1/7
1-1/11
2 x 17/81
9/11 : 5/6
3:12/25
mong mn trả lời giúp ạ
A= 1/3 + 1/3*5 + 1 / 5*7 + ......... + 1 ? 9*11 +1?11*13
1/3*5 + 1/5*7 + 1/7*9 + 1/9*11
nhanh lên nha
bài 1: tính nhanh:
A = 4/1*3*5+4/3*5*7+4/5*7*9+4/7*9*11+4/9*11*13
giúp mik nha !! Mik cảm ơn nhiều
tìm x
1) [(3/8.x-1/2):5/7+4/9].6/11=18/55
2) (7/10-3.x):( 1 9/10-1 2/5)+4/5=1
Tinh nhanh [1/1*3+1/3*5+1/5*7+1/7*9+1/9*11]*y=2/3
Giai ro rang ho minh nhe