B = 1/4 x( 4/ 1x3x5 +4 /3x5x7 +...+ 4/47x49x51)
= 1/4 x( 1/ 1x3 - 1/3x5 +1/3x5 -1/5x7 +...+ 1/47x49 -1/49x51)
= 1/4 x( 1/1x3 -1/49x51)
= 1/4 x( 1/3 - 1/2499)
= 1/4 x 832/2499
= 208 /2499
Vậy B= 208 /2499
C= 1/ 9x11 -1/ 11x13 +1/ 11x13 -1/ 13x15 +... + 1/ 59x61 -1/61x63
= 1/ 9x11 -1/ 61x63
= 1/99 -1/3843
= 416 /42273
Vậy C= 416 /42273
tính nhanh
1+3-5-7+9+11-13-15+17+...-57-59+61+63
tính giá trị biểu thức sau bằng cách hợp lí
(5/4 + 3/4) . 4/7 + (3/4 + 9/4) . 4/7
-3/11 . (-22)/66 . 121/15
3/7 . 2/5 . 7/3 . 20 . 19/72
6/7 . 8/13 + 6/13 . 9/7 - 3/13 . 6/7
-1/4 . 152/11 + 68/4 . (-1)/11
-5/7 . 2/11 + (-5)/7 . 9/11 + 12/7
146/13 - (18/7 + 63/13)
cảm ơn
a)11/53+(32/47+-10/53)+-64/94+1/53+1/3
b) (-1+45/115+47/51)+(-9/23+-1/3)
c) -13/49+12/48+1/12+3/18
d) 13/15+(-4/5+7/18)+-5/12+1/16
Bài 1: Tính
a. 5 × -7/10
b. 4/5 × -3/22
c. 4/9 + 4/3 × 16/4
d. 11/22 - 3/9 × 14/21
Bài 2: Tính hợp lý
A = 6/13 × 5/7 + 6/13 × 2/7 + 17/13
B = 11/15 × 4/11 + 11/15 × 5/11 + 11/15 × 2/11
C = ( 19/64 - 33/22 + 24/51 ) × ( 1/5 - 1/15 - 2/15 )
D = 8/13 × 7/12 + 8/13 × 5/12 - 1/12
Tinh :C=4/9×11×13+4/11×13×15+...+4/59×61×63
1+2+3+........+n
1+3+5+7+.....(2n - 1)
2+4+6+8+....+2n
1+6+11+16+.......+46+51
2+5+11+.......+47+56
3+12+48+.......+3072+12288
2+5+7+12+........+81+131
49-51+53-55+57-59+61-63+65
Bạn nào biewts giúp mk với
Bài 1 Tính nhanh
a) -3/7 + 5/13 + 3/7
b) -5/21+-2/21+8/24
c) -5/11+(-6/11+2)
d) (-1/32+1/2)+15/32
e)5/17+ -6/13 + 3/4 + 7/-13+12/17
f) 7/23+-18/18+-4/9+16/23+-5/8
g)1/3+-3/4+3/5+-1/36+1/15+-2/9
h)-1/2+1/3+-1/4+-2/8+4/18+4/9
1, 1-5+9-13+...+145-149
2, 19-23+27-31+...+203-207
3, 12-17+22-27+....+502-507
4, 3-8+13-18+....+213-218
5, 1-2-3+4+5-6-7+8+9-10-11+12+....+61-62-63+64
6, 3-7-11+15+19-23-27+31+....+339-343-347+351
Giup đỡ mình nhé! Giải nhanh giùm nhé!
