Tính:
A = 8.(32+1).(34+1)...(316+1)
Tính nhanh giá trị biểu thức sau:
4.(32 + 1)(34 + 1)(38 + 1)(316 + 1)
\(4\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)\)
\(=\dfrac{1}{2}\left(3^2-1\right)\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)\)
\(=\dfrac{1}{2}\left(3^4-1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)\)
\(=\dfrac{1}{2}\left(3^8-1\right)\left(3^8+1\right)\left(3^{16}+1\right)\)
\(=\dfrac{1}{2}\left(3^{16}-1\right)\cdot\left(3^{16}+1\right)\)
\(=\dfrac{1}{2}\left(3^{32}-1\right)\)
Tính nhanh:
(3 + 1)(32 + 1)(34 + 1)(38 + 1)(316 + 1)
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\(\left(3+1\right)\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)=\dfrac{1}{2}\left(3-1\right)\left(3+1\right)\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)=\dfrac{1}{2}.\left(3^2-1\right)\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)=\dfrac{1}{2}\left(3^{32}-1\right)=\dfrac{3^{32}}{2}-\dfrac{1}{2}\)
\(\left(3+1\right)\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)\)
\(=\dfrac{\left(3^2-1\right)\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)}{2}\)
\(=\dfrac{3^{32}-1}{2}\)
So sáng A và B:
a)A=(3+1)(32+1)(34+1)(38+1)(316+1) và B=332-1
b)A=2011.2013 và B=20122
a) \(A=\left(3+1\right)\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)=\dfrac{1}{2}\left(3-1\right)\left(3+1\right)\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)=\dfrac{1}{2}\left(3^2-1\right)\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)=\dfrac{1}{2}\left(3^{32}-1\right)< 3^{32}-1=B\)
b) \(A=2011.2013=\left(2012-1\right)\left(2012+1\right)=2012^2-1< 2012^2=B\)
2.4.(32+1).(34+1)......(316+1)
Tính giá trị biểu thức sau bằng 1 cách hợp lí
C1:
a, 3.7.23 - 21 . (- 17)
b, 7.6.3 -7.[(-34)+18]
c, 71.64+32 .(-7)-13.32
d, 13.(23-17)-13.(23+17)
e, (29-9). (-9)+ (-13-7).21
g, (-157).(127-316)-127.(316-157)
Helpppppppp●
a, 3.7.23 - 21.(-17)
= 21.23 + 21.17
= 21.(23 + 17)
= 21.40
= 840
b, 7.6.3 - 7.[(-34) + 18)]
= 7.18 - 7.18 + 34.7
= 34.7
= 238
c, 71.64 + 32.(-7) - 13.32
= 71. 32 . 2 - 7.32 - 32. 13
= 32.(71.2 - 7 - 13)
= 32. (142 - 20)
= 32.122
= 3904
d, 13.(23 - 17) - 13.(23 + 17)
= 13.23 - 13.17 - 13.23 - 13.17
= (13.23 - 13.23) - (13.17 + 13.17)
= - 2.13.17
= - 26.17
= -442
e, (29 - 9).(-9) + (-13 - 7).21
= 20.(-9) - 20.21
= -20.(9 + 21)
= -20.30
= - 600
So sánh:
a) A=2005.2007 B=20062
b)(2+1)(22+1)(24+1)(28+1)(216+1) B=232
c)(3+1)(32+1)(34+1)(38+1)(316+1) B=332-1
So sánh :
a) A = 2005.2001 và B = 20062
b) B = (2 + 1)(22 + 1)(24 + 1)(28 + 1)(216 + 1) và B = 232
c) C = (3 + 1)(32 + 1)(34 + 1)(38 + 1)(316 + 1) và B = 332 - 1
a) Ta có : 2005.2007 = (2006 - 1)(2006 + 1) = 20062 - 12 = 20062 - 1 ( cái khúc này sửa : 2005.2001 thành 2005.2007)
Mà B = 20062
=> 20062 - 1 < 20062
=> A < B
b) Ta có : B = (2 + 1)(22 + 1)(24 + 1)(28 + 1)(216 + 1)
B = (2 - 1)(2 + 1)(22 + 1)(24 + 1)(28 + 1)(216 + 1)
B = (22 - 1)(22 + 1)(24 + 1)(28 + 1)(216 + 1)
B = (24 - 1)(24 + 1)(28 + 1)(216 + 1)
B = (28 - 1)(28 + 1)(216 + 1) = (216 - 1)(216 + 1) = 232 - 1
Mà C = 232
=> B < C
c) Tương tự như câu b
tính nhanh:
1+2-3-4+5+6-7-8+...-31-32+33+34
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