biet n! =1*2**3*...*n . tinh 1*1!+2*2!+3*3!+4*4!+5*5!=?
tinh n biet
1+2+3+4+5+6.....+n=1275
( 1 + n ) . n = 1275 . 2 = 2550
Mà 2550 = 50 . 51
=> n = 50
(1+n).n=1275.2=2550
Mà 2550 = 50.51
=>n = 50
Cái này mk giải chi tiết hơn một chút nha ! ^-^
1+2+3+4+5+6...+n=(n+1)n:2
(n+1)n:2 = 1275
=>(n+1)n = 1275x2
=>(n+1)n = 2550
Do 2550 = 2.3.5.5.17
=>(n+1)n = 50.51
=> n = 50
biiet n!=1*2*3*4........................n;
tinh 1*1!2*2!3*3!4*4!5*5!
1!=1
2!=2
3!=6
4!=24
5!=120
1*1!*2*2!*3*3#*4*4!*5*5! = 5!*2!*3!*4!*5! = 120*2*6*24*120 = 4147200
biet n!=1.2.3....n.tinh 1. 1 ! +2 . 2 ! +3 . 3 ! +4 . 4 !+ 5 . 5 ! =.................................
biet n!=1.2.3...5.1:1!+2:2!+3:3!+4:4!+5:5!=
Cau 1: Tim n biet : 5/8 + 5/24 + 5/48 + 5/80 + ... + 5/2n + 2 . 2n + 4 = 189/112
Cau 2 : Cho A = 1 + 1/1.2 + 1/1.2.3 + ... + 1/1.2.3...2014. So sanh A voi 2
Cau 3 : Tim n biet : 5/3 + 5/15 + 5/35 + 5/63 +...+ 5/2n + 1 . 2n + 3 = 172/69
tinh A/B, biet
A=1/2*32+1/3*33+1/4*34+...+1/n*(n+30)+...+1/1973*2003
B=1/2*1974+1/3*1975+1/4*1976+...+1/n*(n+1972)+...+1/31*2003.
1/2+1/3+2/3+1/4+2/4+3/4+1/5+2/5+3/5+4/5+...+1/n+2/n+3/n+...+n-1/n
tim x biet,
5x + 5x+2= 650
Thuc hien phep tinh
(1+2+3+4+...+90).(12.34 - 6.68) : (1/3+1/4+1/5+1/6)
ta có 5^x+5^x*25=650 suy ra 5^x *26=650 ,5^x=25 suy ra x=2
Mk giúp phần đầu nhé!
Có 5x+5x+2=650
=> 5x.(1+52)=650
5x. 26=650
5x=650:26
5x=25
=> x=2
12*34=1*68
=>12*34-6*68=0=>bieu thuc = 0
1/2+1/3+2/3+1/4+2/4+3/4+1/5+2/5+3/5+4/5+...+1/n+2/n+3/n+...+n-1/n