Đặt \(A=\frac{1}{5}+\left(\frac{1}{5}\right)^2+...+\left(\frac{1}{5}\right)^{50}\)
\(5.A=1+\frac{1}{5}+...+\left(\frac{1}{5}\right)^{49}\)
\(5.A-A=\left(1+\frac{1}{5}+...+\left(\frac{1}{5}\right)^{49}\right)-\left(\frac{1}{5}+\left(\frac{1}{5}\right)^2+...+\left(\frac{1}{5}\right)^{50}\right)\)
\(4.A=1-\frac{1}{5^{50}}< 1\)
\(\Rightarrow A< \frac{1}{4}\)
Tính
A=13/21.2/11+13/21.9/11+8/21.
B=(1-1/5).(1-2/5).(1-3/5)...(1-9/5)
C= (1-1/2).(1-1/3).(1-1/4)...(1-1/50)
D= 2²/1.3 . 3²/2.4 . 4²/3.5 . 5²/4.6 . 6²/5.7
A=2 mũ 3 + 2 mũ 4 + 2 mũ 5 + 2 mũ 6 + 2 mũ 7 +.....+ 2 mũ 90
B=1+5+5 mũ 2 + 5 mũ 3 +5 mũ 4 +......+5 mũ 50
C=1/5 +1/5 mũ 2 + 1/5 mũ 3 + 1/5 mũ 4 +1/5 mũ 6 +......+1/5 mũ 102
D=1/5 +1/5 mũ 3 + 1/5 mũ 4 +1/5 mũ 5 + 1/5 mũ 6 +1/5 mũ 105
bài 7: tính nhanh
a) A = 1 + 2 + 3 + 4 + ... + 50
b) B = 2 + 4 + 6 + 8 + ... + 100
c) C = 1 + 3 + 5 + 7 + ...+ 99
d) D = 2 + 5 + 8 + 11 + ... + 98
e) E = 1 + 2 + 3 + 4 + ... + 25
f) F = 2 + 4 + 6 + 8 + ... + 50
g) G = 3 + 5 + 7 + 9 + ... + 51
h) H = 1 + 5 + 9 + 13 + ... + 81
nhanh nha, giải thik rõ nha, thì mik tick cho
1)tính nhanh
a)(7/4*-4/5+7/2*1/5)*50%-0,1
b)(2/1/3+3/1/2)*0,2+25%
c)2/3+1/3*(-4/9+5/6):7/12
a)5/6+7/12-2/3=
b)3/4-1 1/2+50%:5/12=
c)2/7. 5 1/4-2/7.3 1/4
Cần gấp
1) a) (7/4 . -4/5 +7/2 .-1/5) .50% -0,1
b) (2 1/3 + 3 1/2 ) .0,2 +25%
c) /2 / +/-5/-/-3/+2000^0
giúp zới , giúp zới
Tìm x biết.
a,(3x-10)*-1/2x+5=0
b,-5x*(x+1/5)-1/2*(x+5)=-x+1/5
c,2*|1/2x-1/3|-3/2=1/4
d,|20/9-x|=1/12+1/20+1/30+1/42+1/56+1/72
e,1/2*3*x+1/3*4*x+1/4*5*x+.....+1/49*50*x=1
MÌNH CẦN GẤP.
(2/3 -1/4 +5/11) : (5/12 +1 -7/11)
(-1/2)2-(-2) 2 -50
12 và 1/3 -5/7 :( 24 -23 và 5/7 )
1/1*2*3*4+1/2*3*4*5+1/3*4*5*6+...+1/47*48*49*
50
