(3+1)(3^2+1)(3^4+1)(3^8+1)(3^16+1)(3^32+1)
tính nhanh p/s 1+ 5/4 + 5/8 + 5/16 + 5/32 + 5/64
b) 1/3 +1/9 + 1/27 + 1/81 +...........+ 1/59049
c) 3/2 + 3/8 + 3/32 +3/128 + 3/512
d) 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256 giúp mình với
b: A=1/3+1/9+...+1/3^10
=>3A=1+1/3+...+1/3^9
=>A*2=1-1/3^10=(3^10-1)/3^10
=>A=(3^10-1)/(2*3^10)
c: C=3/2+3/8+3/32+3/128+3/512
=>4C=6+3/2+...+3/128
=>3C=6-3/512
=>C=1023/512
d: A=1/2+...+1/256
=>2A=1+1/2+...+1/128
=>A=1-1/256=255/256
CMR
1/2-1/4+1/8-1/16+1/32-1/64<1/3
1/3-2/3^2+3/3^3+4/3^4+...+99/3^99<3/16
1.Chứng minh rằng a)1/2-1/4+1/8-1/16+1/32-1/64<1/3 b)1/3-2/3^2+3/3^3-4/3^4+...+99/3^99-100/3^100<3/16
(3+1)*(3^2+1)*(3^4+1)*(3^8+1)*(3^16+1)*(3^32+1)
\(A=\left(3+1\right)\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)\left(3^{32}+1\right)\)
\(2A=\left(3^2-1\right)\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)\left(3^{32}+1\right)\)
\(2A=\left(3^4-1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)\left(3^{32}+1\right)\)
\(2A=\left(3^8-1\right)\left(3^8+1\right)\left(3^{16}+1\right)\left(3^{32}+1\right)\)
\(2A=\left(3^{16}-1\right)\left(3^{16}+1\right)\left(3^{32}+1\right)\)
\(2A=\left(3^{32}-1\right)\left(3^{32}+1\right)\)
\(2A=3^{64}-1\Rightarrow A=\dfrac{3^{64}-1}{2}\)
A=(3^2+1).(3^4+1).(3^8+1).(3^16+1)-3^32/2 (3^32/2 là phân số nha)
mọi người giúp emvới
Lời giải:
8A=(3^2-1)(3^2+1)(3^4+1)(3^8+1)(3^{16}+1)-4.3^{32}$
$=[(3^2-1)(3^2+1)](3^4+1)(3^8+1)(3^{16}+1)-4.3^{32}$
$=(3^4-1)(3^4+1)(3^8+1)(3^{16}+1)-4.3^{32}$
$=(3^8-1)(3^8+1)(3^{16}+1)-4.3^{32}$
$=(3^{16}-1)(3^{16}+1)-4.3^{32}$
$=3^{32}-1-4.3^{32}$
$=-3.3^{32}-1=-3^{33}-1$
$\Rightarrow A=\frac{-3^{33}-1}{8}$
CMR:
a)1/2-1/4+1/8-1/16+1/32-1/64<1/3
b)1/3 - 2/3^2 + 3/3^3 - 4/3^4 +...+ 99/3^99 -100/3^100 < 3/16
cmr
a) 1/2 -1/4+1/8-1/16+1/32-1/64 <1/3
b) 1/3-2/3^2+3/3^3-4/3^4+...+99/3^99-100/3^100<3/16
Chứng minh rằng:
a) 1/2-1/4+1/8-1/16+1/32-1/64<1/3
b) 1/3-2/3^2+3/3^3-3/3^4+...+99/3^99-100/3^100<3/16
Rút gọn biểu thức: (3+1)(3^2+1)(3^4+1)(3^8+1)(3^16+1)(3^32+1)
goi y nha A=1/2.(3^2-1)(3^2+1)....(3^32+1)