So sánh P và Q biết:
P=20/30+20/70+20/126+....+20/798 Q=(31/2 . 32/2 . 33/2.....60/2):(1.3.5....59)
Có lời giải nhé!
So sánh Q, P biết :
P = \(\dfrac{20}{30}\) + \(\dfrac{20}{70}\) + \(\dfrac{20}{126}\) + ... + \(\dfrac{20}{798}\)
Q = (\(\dfrac{31}{2}\) . \(\dfrac{32}{2}\) . \(\dfrac{33}{2}\) ... \(\dfrac{60}{2}\)) : ( 1.3.5...55)
A=31/2*32/2...*60/2
B=1*3*5*...*59
C=20/30+20/70+20/126+....+20/798
CMR:C>A:B
đố làm được
Bài 1: So sánh
\(M=\frac{20^{30}+2}{20^{31}+2}\) và \(N=\frac{20^{31}+2}{20^{32}+2}\)
Vì N<1
=> N= 20^31+2/20^32+2
<20^31+2+38/ 20^32+2+38
=20^31+40/ 20^32+40
=20.(20^30+2) / 20.(20^31+2)
=20^30+2 / 20^32+2 = M
Vậy N<M
\(N=\frac{20^{31}+2}{20^{32}+2}=\frac{20^{31}+2+18}{20^{32}+2+18}=\frac{20^{31}+20}{20^{32}+20}=\frac{10.\left(20^{30}+2\right)}{10.\left(20^{31}+2\right)}\)\(=M\)
\(\Rightarrow M=N\)
1, tim x bết:
,\(\frac{\left(-5^4\right).\left(-15^2\right)-5^4.\left(-3^2.5\right)}{\left(-3^4\right).25^2-\left(-15^2\right).225.5}\)\(:\)\(\frac{x}{5}\)\(=\frac{-1}{6}\)
2, cho A=\(\frac{20}{30}+\frac{20}{70}+\frac{20}{126}+...+\frac{20}{798}\)
B=\(\left(\frac{41}{2}.\frac{42}{2}.\frac{43}{2}...\frac{80}{2}\right):\left(1.3.5...79\right)\)
So sánh A và B.
3, Tính nhanh.
\(\frac{0,875+\frac{1}{2}-7\%-\frac{1}{58}}{\frac{1}{25}-\frac{1}{2}-\frac{2}{7}+\frac{2}{203}}\)\(-125\%\)
HELP ME PLEASE......
c=20/30+20/70+20/126+....+20/798
nhanh lên nhé
Tính giá trị biểu thức sau :
\(\frac{20}{30}+\frac{20}{70}+\frac{20}{126}+...+\frac{20}{798}\)
So sánh P và Q , biết rằng
P=31/2×32/2×33/2×......×60/2 và Q=1×3×5×.....×59?
CMR: \(\frac{31}{2}.\frac{32}{2}.\frac{33}{2}.....\frac{60}{2}=1.3.5.....59\)
\(\frac{31}{2}\)\(.\)\(\frac{32}{2}\)\(.\)\(\frac{33}{2}\)\(....\)\(\frac{60}{2}\)
\(=\)\(\left[\left(31.32.33....60\right)\right]\)\(.\)\(\left(\frac{1.2.3....30}{2^{30}}\right)\)\(.\)\(\left(1.2.3....30\right)\)
\(=\)\(\left[\frac{\left(1.3.5....59\right).\left(2.4.6....60\right)}{2.4.6....60}\right]\)\(=\)\(1.3.5....59\)
Vậy \(\frac{31}{2}\)\(.\)\(\frac{32}{2}\)\(.\)\(\frac{33}{2}\)\(....\)\(\frac{60}{2}\)\(=\)\(1.3.5....59\)
ta có:Đặt A= \(1.3.5.....59=\frac{1.2.3.4.....59.60}{2.4.6.....60}\)
=\(\frac{1.2.3.....59.60}{2^{30}.\left(1.2.3.....30\right)}=\frac{31.32.....59.60}{2^{30}}\)
= \(\frac{31}{2}.\frac{32}{2}.....\frac{59}{2}.\frac{60}{2}\)
vì \(\frac{31}{2}.\frac{32}{2}.....\frac{59}{2}.\frac{60}{2}\) = \(\frac{31}{2}.\frac{32}{2}.....\frac{59}{2}.\frac{60}{2}\)
\(\Rightarrow\)A= \(\frac{31}{2}.\frac{32}{2}.....\frac{59}{2}.\frac{60}{2}\)
( Điều phải chứng minh)
toán nâng cao lớp 6 đấy bạn nha
So sánh \(P=\frac{31}{2}.\frac{32}{2}.\frac{33}{2}...\frac{60}{2}\) và Q=1.3.5.7........59
Ta có:
31/2.32/2.33/2....60/2=31.32......60/2^30
=(31.32.33....60)(1.2.3....30)/2^30(1.2.3...30)
=(1.3.5...59)(2.4.6...60)/(2.4.6...60)=1.3.5...59
=>P=Q
nhớ ****
cái dòng 3, 4 mk ko hiểu sao 2^30.(1.2.3....30) lại bằng 2.4.6...60