KHẨN CẤP!!!
(2+4+6+8+...+98+100)x 10/2+4+8+16+...+512-2
Tính :
N = ( 1/2x4 + 1/4x6 + 1/6x8 + 1/8x10 + ....... + 1/98 X 100 ) : ( 1/2 + 1/4 + 1/8 + 1/16 + ........ + 1/512 )
1 + 2 + 4 + 8 + 16 + 32 + ... + 1024 + 2048 + 4096 =?
KHẨN CẤP! KHẨN CẤP!
Đặt \(A=1+2+4+.........+4096\)
\(2A=2+4+8+......+8192\)
\(\Rightarrow2A-A=8192-1\)
\(\Rightarrow A=8191\)
Đặt \(S=1+2+4+...+1024+2048+4096\)
\(S=1+2^1+2^2+2^3+....+2^{10}+2^{11}+2^{12}\)
\(2S=2+2^2+2^3+....+2^{11}+2^{12}+2^{13}\)
\(2S-S=\left(2+2^2+2^3+....+2^{12}+2^{13}\right)-\left(1+2+2^2+....+2^{11}+2^{12}\right)\)
\(S=2^{13}-1=8192-1=8191\)
A=1+2+4+8+16+.....+1024+2048+4096
2A= 2+4+8+16+32+....+2048+4096+8192
2A-A=A=2+4+8+16+32+....+4096+8192-(1+2+4+8+16+...+1024+2048+4096)
A=8192-1
A=8191 k nha
(2 + 4 + 6 + ... + 98) x (\(\dfrac{3}{4}\) x 8 - 15 x 0,4) x (\(\dfrac{1}{2}\) + \(\dfrac{1}{4}\) + \(\dfrac{1}{8}\) + ... + \(\dfrac{1}{512}\) )
Giúp mình vớiii
\(=\left(2+4+6+...+98\right)\left(6-6\right)\left(\dfrac{1}{2}+\dfrac{1}{4}+...+\dfrac{1}{512}\right)\)
=0
= ( 2+4+6+...+98 ) ( 6- 6) ( 1/2+1/4 + .......+ 1/ 512 )
= 0
Chúc bạn học tốt
= (2 + 4 + 6 + ... + 98) x ( 6 - 6 ) x ( \(\dfrac{1}{2}\) + \(\dfrac{1}{4}\) + \(\dfrac{1}{8}\) +...+ \(\dfrac{1}{512}\))
= (2 + 4 + 6 + ... + 98) x 0 x ( \(\dfrac{1}{2}\) + \(\dfrac{1}{4}\) + \(\dfrac{1}{8}\) +...+ \(\dfrac{1}{512}\))
= 0
*****Vì số nào nhân với 0 cũng bằng 0
Tính nhanh
a) 1994 x 808 + 1995 x 192
b) 2 - 4 + 6 - 8 + 10 - 12 + 14 - 16 + 18 - .... + 98 - 100 + 102
a)1994x808+1995x192
=1994x808+(1994+1)x192
=1994x808+1994x192+1x192
=1994x(808+192)+192
=1994x1000+192
=1994000+192
=1994192
b)Dãy phép tính đó có:(102-2):2+1=51(số)
Chia 50 số đầu tiên thành 25 nhóm (mỗi nhóm 2 số),ta được:
2-4+6-8+10-12+14-16+18-...+98-100+102
=(2-4)+(6-8)+(10-12)+(14-16)+...+(98-100)+102
=(-2)+(-2)+(-2)+(-2)+...+(-2)+102
=(-2)x25+102
=-50+102
=52
a) 1994 x 808 + 1995 x 192
= 1995 x ( 808 + 192 )
= 1995 x 1000
= 1995000
Tính nhanh
a) 27 x 45 + 55 x 27/ 2 + 4 + 6 + 8 + ... + 16 + 18
b) 3737 x 43 - 4343 x 37/ 2 + 4 + 6 + 8 + ... + 98 + 100
a) \(\frac{27.45+55.27}{2+4+6+8+...+16+18}=\frac{27.\left(45+55\right)}{\left(2+18\right)+\left(16+4\right)+\left(14+6\right)+\left(12+8\right)}\)
\(=\frac{27.100}{20+20+20+20}=\frac{2700}{20.4}=\frac{2700}{80}=\frac{135}{4}\)
b) Lười
Làm giống câu a nhé
1 200-18 :(372:3 *x-1)-28=166
(7*13+8*13):(9va2/3-x)=39
x=(6va3/5:s6-0,125 *8+2va2/15*0,03)*11/4
(100-99+98-97+96-95+....+4-3+2-1):50 +2010-12*x=91
2 A= 1/2+1/4+1/8+1/16+1/32+1/64+1/128+1/256+1/512+1/1024
B=27.45+27.55/2+4+...+16+18
A= 1/2 x 4 + 1/4 x 6 + 1/6 x 8 +1/8 x 10 + ... +1/98 x 100
2A=2/2x4+2/4x6+..+2/98x100
=> 2A=1-1/4+1/4-1/6+..+1/98-1/100
=> 2A=1-1/100
=> 2A=99/100
=> A=99/100:2
=> A=99/200
tính nhanh
a, 1-2+3-4+5-6+......+101-102+103
b, 2-4+6-8+10-21+.....+98-100+102
c, 16-18+20-22+.....+64-66+68
( 2 - 4 + 6 - 8 + 10 - 12 + ... + 98 - 100 ) + x = 1972
Lời giải:
$(2-4+6-8+10-12+...+98-100)+x=1972$
$(2-4)+(6-8)+..+(98-100)+x=1972$
$(-2)+(-2)+....+(-2)+x=1972$
$(-2).25+x=1972$
$-50+x=1972$
$x=2022$