1. Viết các phép tính sau dưới dạng lũy thừa của một số :
a, 28 . 2 . 4
b, 85 : 64
c, 37 : 9
d, 917 . 81
e, x6 . x . x2
2. Tìm x :
a, 2x - 15 = 17
b, 2 . 3x = 162
c, 5 . x . 52 = 10
d, 5 . x2 - 1 = 124
3. Tính giá trị biểu thức :
a, 23 - 53 : 52 +12 . 22
b, 5 . 22. 23 - 4 . [58 : 56 ]
c, 32 - 25 : 23 + 20160
d, [ 62016 - 62015 ] : 62014
CÓ 3 BÀI THÔI CÁC BẠN GIÚP MÌNH VỚI NHÉ !!! MÌNH XIN CÁM ƠN !!!
Bài 1:
a) \(2^8.2.4=2^9.2^2=2^{11}\)
b) \(8^5:64=8^5:8^2=8^3\)
c) \(3^7:9=3^7:3^2=3^5\)
d) \(9^{17}.81=9^{17}.9^2=9^{19}\)
e) \(x^6.x.x^2=x^9\)
Bài 2:
a) \(2^x-15=17\)
\(\Rightarrow2^x=32\)
\(\Rightarrow2^x=2^5\)
\(\Rightarrow x=5\)
Vậy x = 5
b) \(2.3^x=162\)
\(3^x=162:2\)
\(3^x=81\)
\(\Rightarrow3^x=3^4\)
\(\Rightarrow x=4\)
Vậy x = 4
c) \(5.x.5^2=10\)
\(\Rightarrow x.5^3=10\)
\(\Rightarrow x.125=10\)
\(\Rightarrow x=10:125\)
\(\Rightarrow x=\frac{2}{25}\)
Vậy \(x=\frac{2}{25}\)
d) \(5.x^2-1=124\)
\(\Rightarrow5.x^2=125\)
\(\Rightarrow x^2=125:5\)
\(\Rightarrow x^2=5^2\)
\(\Rightarrow x=\pm5\)
Vậy \(x=\pm5\)
Câu 1:
a)28.2.4=28.2.22=211
b)85:64=85:82=83
c)37:9=37:32=35
d)917.81=917.92=919
e)x6.x.x2=x9
Câu 2:
a)2x-15=17
2x=15+17
2x=32=26
Vậy x=6
b)2.3x=162
3x=81=34
Vậy x=4
c)5.x.52=10
53.x=10
x=10:53
x=\(\frac{2}{25}\)
Vậy x=\(\frac{2}{25}\)
d)5.x2-1=124
x=124:5
x=\(\frac{124}{5}\)
Vậy x=\(\frac{124}{5}\)
Câu 3:
a)23-53:52+12.22=23-5+48=3+48=51
b)5.22.23-4.(58:56)=5.25-4.52=160-100=60
c, 32 - 25 : 23 + 20160=32-22+1=5+1=6
d)(62016-62015):62014=62016:62014-62015:62014=62-6=30
Bài 1:
a) 28.2.4=28.2.22=211
b)85:64=(23)5:26=215:26=211
c)37:9=37:32=35
d)917.81=(32)17.34=334.34=338
e)x6.x.x2=x9
Bài 2:
a)2x-15=17
=>2x=17-15
=>2x=21
=>x=1
Vậy x=1.
b)2.3x=162
=>2.3x=2.34
=>3x=34
=>x=4
Vậy x=4
c)5.x.52=10
=>53.x=10
=>125.x=10
=>x=10:25=\(\frac{10}{125}\)=\(\frac{2}{25}\)
Vậy x=\(\frac{2}{25}\)
d)5.x2-1=124
=>5.x=124
=>x=\(\frac{124}{5}\)
Vậy x=\(\frac{124}{5}\)
Bài 3:
a)23-53:52+12.22
=23-5+22.3.22
=8-5+24.3
=3+24.3
=3.(1+24)
=3.(1+16)
=3.17
=51
b)5.22.23-4.(58:56)
=5.25-4.52
=5.25-22.52
=5.22.(23-5)
=5.4.(8-5)
=20.3
=60
c)32-25:23+20160
=9-22+1
=9-4+1
=5+1
=6
d)(62016-62015):62014
=62016:62014-62015:62014
=62-6
=36-6
=30
a) = 29.22 = 211
b) = 85 : 82 = 83
c) = 37 : 32 = 35
d) = 917 . 92 = 919
e) =