c) 64.4x =168
tìm x
64.4x=168
\(64\cdot4^x=16^8\)
\(\Rightarrow4^3\cdot4^x=\left(4^2\right)^8\)
\(\Rightarrow4^{x+3}=4^{16}\)
\(\Rightarrow x+3=16\)
\(\Rightarrow x=16-3\)
\(\Rightarrow x=13\)
Vậy : x=13
Câu 3: Tìm x ∈ N, biết:
a) 3 x . 3 = 243 b) 2 x . 162 = 1024 c) 64.4x = 168 d) 2 x = 16Câu 4 : Tìm x, biết. a) 2 x .4 = 128 b) (2x + 1)3 = 125 c) 2x – 2 6 = 6 d) 49.7x = 24013:
a: 3^x*3=243
=>3^x=81
=>x=4
b; 2^x*16^2=1024
=>2^x=4
=>x=2
c: 64*4^x=16^8
=>4^x=4^16/4^3=4^13
=>x=13
d: 2^x=16
=>2^x=2^4
=>x=4
Bài 4 : Tìm x là số tự nhiên , biết.
a) 3x . 3 = 243 b) 64.4x = 168
c) 34.3x = 37 d) (2x + 1)3 = 125
a/ 3x . 3 = 243
9x = 243
x = 243 : 9
x = 27
a) x= 27
b) x= \(\frac{21}{32}\)
c) x =\(\frac{37}{102}\)
d) x=\(\frac{61}{3}\)
b/ 64.4x = 168
256 . x = 168
x = 168 : 256
x = 21/32
c/ 34.3x = 37
102 . x = 37
x = 37 : 102
x = 37/102
d/ ( 2x + 1 ) ^3 = 125
2x + 1 = 5
2x = 5 - 1
2x = 4
x = 4 : 2
x = 2
Bài toán 7 : Tìm x N, biết.
a) 3x . 3 = 243 | b) 2x . 162 = 1024 | c) 64.4x = 168 | d) 2x = 16 |
a) \(3^x\cdot3=243\)
\(\Rightarrow3^{x+1}=243\)
\(\Rightarrow3^{x+1}=3^5\)
\(\Rightarrow x+1=5\)
\(\Rightarrow x=4\)
b) \(2^x\cdot162=1024\)
Xem lại đề
c) \(64\cdot4^x=168\)
Xem lại đề
d) \(2^x=16\)
\(\Rightarrow2^x=2^4\)
\(\Rightarrow x=4\)
a: =>3^x=81
=>x=4
b: =>2^x=1024/16^2=4
=>x=2
c: =>4^x=16^8/64=4^16/4^3=4^13
=>x=13
a) 2x.4 = 128
b) (2x + 1)3 = 125
c) 2x – 26 = 6
d) 64.4x = 45
e) 27.3x = 243
g) 49.7x = 2401
h) 3x = 81
k) 34.3x = 37
n) 3x + 25 = 26.22 + 2.30
a) \(2^x\cdot4=128\)
\(\Rightarrow2^x\cdot2^2=2^7\)
\(\Rightarrow2^{x+2}=2^7\)
\(\Rightarrow x+2=7\)
\(\Rightarrow x=5\)
b) \(\left(2x+1\right)^3=125\)
\(\Rightarrow\left(2x+1\right)^3=5^3\)
\(\Rightarrow2x+1=5\)
\(\Rightarrow2x=4\)
\(\Rightarrow x=4:2\)
\(\Rightarrow x=2\)
c) \(2x-2^6=6\)
\(\Rightarrow2x-64=6\)
\(\Rightarrow2x=70\)
\(\Rightarrow x=70:2\)
\(\Rightarrow x=35\)
d) \(64\cdot4^x=45\)
\(\Rightarrow4^3\cdot4^x=45\)
\(\Rightarrow4^{x+3}=45\)
Xem lại đề
e) \(27\cdot3^x=243\)
\(\Rightarrow3^3\cdot3^x=3^5\)
\(\Rightarrow3^{x+3}=3^5\)
\(\Rightarrow x+3=5\)
\(\Rightarrow x=2\)
g) \(49\cdot7^x=2401\)
\(\Rightarrow7^2\cdot7^x=7^4\)
\(\Rightarrow7^{x+2}=7^4\)
\(\Rightarrow x+2=4\)
\(\Rightarrow x=2\)
h) \(3^x=81\)
\(\Rightarrow3^x=3^4\)
\(\Rightarrow x=4\)
k) \(3^4\cdot3^x=3^7\)
\(\Rightarrow3^{x+4}=3^7\)
\(\Rightarrow x+4=7\)
\(\Rightarrow x=3\)
n) \(3^x+25=26\cdot2^2+2\cdot3^0\)
\(\Rightarrow3^x+25=104+2\)
\(\Rightarrow3^x+25=106\)
\(\Rightarrow3^x=81\)
\(\Rightarrow3^x=3^4\)
\(x=4\)
`@` `\text {Ans}`
`\downarrow`
`a)`
`2^x*4 = 128`
`=> 2^x = 128 \div 4`
`=> 2^x = 2^7 \div 2^2`
`=> 2^x = 2^5`
`=> x = 5`
Vậy, `x = 5.`
`b)`
\(\left(2x+1\right)^3=125\)
`=> (2x + 1)^3 = 5^3`
`=> 2x + 1 = 5`
`=> 2x = 5-1`
`=> 2x = 4`
`=> x = 4 \div 2`
`=> x = 2`
Vậy, `x = 2`
`c)`
\(2x-2^6=6\)
`=> 2x = 6+2^6`
`=> 2x = 70`
`=> x = 70 \div 2`
`=> x = 35`
Vậy, `x = 35`
`d)`
\(64\cdot4^x=45\) Bạn xem lại đề
`e)`
`27*3^x = 243`
`=> 3^3 * 3^x = 3^5`
`=> 3^(3 + x) = 3^5`
`=> 3 + x = 5`
`=> x = 5 - 3`
`=> x = 2`
Vậy, `x = 2`
`g)`
`49* 7^x = 2401`
`=> 7^2 * 7^x = 7^4`
`=> 7^(2 + x) = 7^4`
`=> 2 + x = 4`
`=> x = 4 - 2`
`=> x = 2`
Vậy, `x = 2`
`h)`
`3^x = 81`
`=> 3^x = 3^4`
`=> x = 4`
Vậy, `x = 4`
`k)`
`3^4 * 3^x = 3^7`
`=> 3^(4 + x) = 3^7`
`=> 4 + x = 7`
`=> x = 7 - 4`
`=> x = 3`
Vậy, `x = 3`
`n)`
`3^x + 25 = 26*2^2 + 2*3^0`
`=> 3^x + 25 = 104 + 2`
`=> 3^x + 25 = 106`
`=> 3^x = 106 - 25`
`=> 3^x = 81`
`=> 3^x = 3^4`
`=> x = 4`
Vậy, `x = 4.`
\(#48Cd\)
Tìm x, biết :
a. 70 - 5. ( x - 3 ) = 45
b. 10 + 2.x = 45 : 43
c. 60 - 3 .x - 2 = 51
d. 4.x - 20 = 25 : 23
e. 2x.4 = 16
f. 3x.3 = 243
g. 64.4x = 168
h. 2x.162 = 1024
Tách ?
`a, 70 -5.(x-3) =45`
`=> 5.(x-3)= 70-45`
`=> 5.(x-3)=25`
`=>x-3=25:5`
`=>x-3=5`
`=>x= 5+3`
`=>x=8`
______
`b,10 + 2.x = 4^5:4^3`
`=> 10 + 2.x = 4^(5-3)`
`=> 10 + 2.x =4^2=16`
`=> 2.x=16-10`
`=>2.x=6`
`=>x=6:2`
`=>x=3`
_____
`c,60-3.x-2=51`
`=> 60-3.x= 51+2`
`=> 60-3.x=53`
`=>3.x=60-53`
`=> 3.x= 7`
`=>x= 7/3`
____
`d, 4.x-20=2^5:2^3`
`=> 4.x-20=2^(5-3)`
`=> 4.x-20=2^2`
`=> 4.x= 4+20`
`=>4.x=24`
`=>x=24:4`
`=>x=6`
____
`2^x . 4=16`
`=> 2^x=16:4`
`=>2^x= 4`
`=>2^x=2^2`
`=>x=2`
____
`f, 3^x . 3=243`
`=>3^x=243:3`
`=> 3^x=81`
`=> 3^x=3^3`
`=>x=3`
_____
`g, 64. 4^x =16^8`
`=> 4^3 . 4^x=(4^2)^8`
`=> 4^3 . 4^x = 4^(16)`
`=> 4^x= 4^(16-3)`
`=>4^x=4^(13)`
`=>x=13`
_____
`2^x . 16^2 =1024`
`=> 2^x= 1024 : 16^2`
`=>2^x=4`
`=>2^x=2^2`
`=>x=2`
a: =>5(x-3)=25
=>x-3=5
=>x=8
b: =>2x=16-10=6
=>x=3
c: =>58-3x=51
=>3x=7
=>x=7/3
d: =>4x-20=4
=>4x=24
=>x=6
e: =>2^x=4
=>2^x=2^2
=>x=2
f: =>3^x=81
=>3^x=3^4
=>x=4
g: =>4^x*4^3=4^16
=>x+3=16
=>x=13
h: =>2^x=1024/256=4=2^2
=>x=2
Thực hiện các phép tính sau một cách hợp lý:
a,(-168)+(-73).168+(-168).27
b,48.(-21)+(-142).(-24)
e làm xong bài tập cô Hương ra chưa
Tính nhanh:
a, [ 168 .168 - 168 .58 ] : 110
b, [456 . 11 +912] . 37 : 13 . 74
c, [ 45 .16 - 17] : [ 28 + 45 . 15]
a ) [ 168 .168 - 168 . 58 ] : 110
= [ 168 . ( 168 - 58 ) ] : 110
= 168 . 110 : 110
= 168 .1
= 168
a,(-65) + 28 + (-35) + 172
b, 34. (-65) + (-55) .34 + 34 .20
c, 168 - ( 437 + 168 ) + ( -105 + 437)
a)=(-65-35)+(28+172)
=-100+100
=0
b)=34.[-65+(-55)+20)
=34.(-100)
=-3400
c)=168-437-168-105+437
=(168-168)+(-437+437)-105
=0+0-105
-105
a; (-65) + 28 + (-35) + 172
= -(65 + 35) + (28 + 172)
= - 100 + 200
= 100
b; 34.(-65) + (-55).34 + 34.20
= 34.(-65 - 55 + 20)
= 34.(-120 + 20)
= 34.(-100)
= -3400
c; 168 - (437 + 168) + (-105 + 437)
= 168 - 437 - 168 - 105 + 437
= (168 - 168) - (437 - 437) - 105
= 0 - 0 - 105
= -105