9-6+7 = ( bao nhieu )
1/5*6+1/6*7+1/7*8+1/8*9=bao nhieu
1/5*6 + 1/6*7 + 1/7*8 + 1/8*9
= 1/5 - 1/6 + 1/6 - 1/7 + 1/7 - 1/8 + 1/8 - 1/9
= 1/5 - 1/9
= 4/45
=1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1/5-1/9
=4/45
B= 1/3*4 - 1/4*5 - 1/5*6 - 1/6*7 - 1/ 7*8 - 1/8*9 - 1/ 9*10
B bang bao nhieu ?
\(B=\frac{1}{3.4}-\frac{1}{4.5}-\frac{1}{5.6}-\frac{1}{6.7}-\frac{1}{7.8}-\frac{1}{8.9}-\frac{1}{9.10}\)
\(=\frac{1}{3}-\frac{1}{4}-\left(\frac{1}{4}-\frac{1}{5}\right)-\left(\frac{1}{5}-\frac{1}{6}\right)-\left(\frac{1}{6}-\frac{1}{7}\right)-\left(\frac{1}{7}-\frac{1}{8}\right)-\left(\frac{1}{8}-\frac{1}{9}\right)-\left(\frac{1}{9}-\frac{1}{10}\right)\)
\(=\frac{1}{3}-\frac{1}{4}-\frac{1}{4}+\frac{1}{10}\)
\(=\frac{-1}{15}\)
B BANG 8
1+9-6+3-4+7-4+9-1-79+698+3+68-467+659-564-1+97-312-478+649-546=bao nhieu
1+2+3+4+5+6 +7+8+9+....+2015+2016. hoi day tren co bao nhieu chu so 1
x+1+2+3+4+5+6+7+8+9+10+11+...+100=250000
Hoi x bang bao nhieu
x+1+2+3+....+100 = 250000
x + 5050 = 250000
x = 250000 - 5050
x = 2244950
x+1+2+3+....+100 = 250000
x + 5050 = 250000
x = 250000 - 5050
x = 2244950
@@ hacker
x+1+2+3+4+5+6+7+.....+100=250000
suy ra x+(1+100)x100:2=250000
suy ra x+101x50=250000
suy ra x+5050=250000
suy ra x=250000-5050
x=244950
co bao nhieu so co 100 chu so ma moi so ko chia het ch 2 3 4 5 6 7 8 9 10 ?
1+2-3+4-5+6-7+8-9+10...19+20 tinh nhanh bang bao nhieu giai thich cach lam
1+2+3+4+5+6+7.......17+18+19+20=(29+1)×(20:10)
=21×10
=210
bao nhieu so tu 7 den 91 thi bao nhieu so chia het cho 9
1-2+3-4+5-6+7-8+9-10+...+95-96+97-98+99-100=bao nhieu
giải chi tiết cho mình nhé
Đặt A = 1 - 2 + 3 - 4 + 5 - 6 + ......+ 97 - 98 + 99 - 100
<=> A = ( 1 - 2 ) + ( 3 - 4 ) + ( 5 - 6 ) + ...... + ( 97 - 98 ) + ( 99 - 100 )
<=> A = ( - 1 ) + ( - 1 ) + ( - 1 ) + ...... + ( - 1 ) + ( - 1 ) ( Có 50 số )
=> A = ( - 1 ) . 50 = - 50
Vậy A = - 50