Tìm a=7*2+7*7+7*5-7*4
Tìm a=7*2+7*7+7*5-7*4
\(a=7\cdot2+7\cdot7+7\cdot5-7\cdot4\)
\(a=7\cdot\left(2+7+5-4\right)\)
\(a=7\cdot10\)
\(a=70\)
a=7*2+7*7+7*5-7*4
a=14+49+35-28
a=98-28
a= 70
#Trl :
\(a=7\times2+7\times7+7\times5-7\times4\)
\(a=7\times\left(2+7+5-4\right)\)
\(a=7\times10\)
\(a=70\)
a) 5(2x -1) - 4(8 - 3x) = 7
<=> 10x - 5 - 32 + 12x = 7
<=> 22x = 44
<=> x =2
Vậy x = 2 là nghiệm phương trình
b) 7(2x - 5) - 5(7x - 2) + 2(5x - 7) = (x - 2) - (x + 4)
<=> 14x - 35 - 35x + 10 + 10x - 14 = x - 2 - x - 4
<=> -11x - 39 = - 6
<=> -11x = 33
<=> x = -3
Vậy x = -3 là nghiệm phương trình
\(a,10x-5-32+12x=7\)
\(22x=44\)
\(x=2\)
\(b,14x-35-35x+10+10x-14=x-2-x-4\)
\(-11x-39=-6\)
\(-11x=-33\)
\(x=3\)
sửa lại đoạn cuối
\(-11x=33\)
\(x=-3\)
Tìm x
A. 4/5-x=5/7
B. x-3/7=2/3-2/7
C. 7/9-x=1/4+2/9
Tìm x, biết:
a) \(\dfrac{-2}{5}\) + \(\dfrac{4}{5}\) . x = \(\dfrac{3}{5}\)
b) \(\dfrac{-3}{7}\) - \(\dfrac{4}{7}\) : x = \(\dfrac{2}{5}\)
c) \(\dfrac{4}{7}\) . x + \(\dfrac{2}{3}\) = \(\dfrac{-1}{5}\)
d) \(\dfrac{5}{7}\) : x -1 = \(\dfrac{2}{3}\)
a, - \(\dfrac{2}{5}\) + \(\dfrac{4}{5}\).\(x\) = \(\dfrac{3}{5}\)
\(\dfrac{4}{5}\).\(x\) = \(\dfrac{3}{5}\)+ \(\dfrac{2}{5}\)
\(\dfrac{4}{5}\).\(x\) = 1
\(x\) = \(\dfrac{5}{4}\)
b, - \(\dfrac{3}{7}\) - \(\dfrac{4}{7}\): \(x\) = \(\dfrac{2}{5}\)
\(\dfrac{4}{7}\): \(x\) = - \(\dfrac{3}{7}\) - \(\dfrac{2}{5}\)
\(\dfrac{4}{7}\): \(x\) = - \(\dfrac{29}{35}\)
\(x\) = \(\dfrac{4}{7}\): (- \(\dfrac{29}{35}\) )
\(x\) = - \(\dfrac{20}{29}\)
c, \(\dfrac{4}{7}\).\(x\) + \(\dfrac{2}{3}\) = - \(\dfrac{1}{5}\)
\(\dfrac{4}{7}\).\(x\) = -\(\dfrac{1}{5}\) - \(\dfrac{2}{3}\)
\(\dfrac{4}{7}\).\(x\) = - \(\dfrac{13}{15}\)
\(x\) = - \(\dfrac{13}{15}\): \(\dfrac{4}{7}\)
\(x\) = - \(\dfrac{91}{60}\)
d, \(\dfrac{5}{7}\): \(x\) - 1 = \(\dfrac{2}{3}\)
\(\dfrac{5}{7}\): \(x\) = \(\dfrac{2}{3}\)+ 1
\(\dfrac{5}{7}\): \(x\) = \(\dfrac{5}{3}\)
\(x\) = \(\dfrac{5}{7}\): \(\dfrac{5}{3}\)
\(x\) = \(\dfrac{3}{7}\)
A=4/7+5+3/7^2+5/7^3+6/7^4;B=5/7^4+5+6?7^2+4/7+5/7^3 so sanh A va B
Tìm số tự nhiên n, biết : a) 5^n +1 = 625; b) 7^n= 7^2. 7^4; c) 7. 2^3n-1=224
`5^(n + 1) = 625`
`=> 5^(n + 1) = 5^4`
`=> n + 1 = 4`
`=> n = 4 -1`
`=> n = 3`
`7^n = 7^2 . 7^4`
`=> 7^n = 7^(2 + 4)`
`=> 7^n = 7^6`
`=> n = 6`
`7. 2^(3n - 1) = 224`
`=>2^(3n-1) = 224 : 7`
`=> 2^(3n-1) = 32`
`=> 2^(3n -1) = 2^5`
`=> 3n - 1 = 5`
`=> 3n = 6`
`=> n = 2`
a: =>5^(n+1)=5^4
=>n+1=4
=>n=3
b: =>7^n=7^6
=>n=6
c: =>2^(3n-1)=32
=>3n-1=5
=>3n=6
=>n=2
a) \(5^{n+1}=625\)
\(\Rightarrow5^{n+1}=5^4\)
\(\Rightarrow n+1=4\)
\(\Rightarrow n=4-1\)
\(\Rightarrow n=3\)
b) \(7^n=7^2\cdot7^4\)
\(\Rightarrow7^n=7^{2+4}\)
\(\Rightarrow7^n=7^6\)
\(\Rightarrow n=6\)
c) \(7\cdot2^{3n-1}=224\)
\(\Rightarrow2^{3n-1}=224:7\)
\(\Rightarrow2^{3n-1}=32\)
\(\Rightarrow2^{3n-1}=2^5\)
\(\Rightarrow3n-1=5\)
\(\Rightarrow3n=5+1\)
\(\Rightarrow3n=6\)
\(\Rightarrow n=\dfrac{6}{3}\)
\(\Rightarrow n=2\)
Tìm 2 chữ số tận cùng của :
a) 2^10 + 2^2000
b) 7^126 + 9^1991 - [ 7^4 ]^4 + [ 7^4 ]^9 - 7^3
c) 5^2015 - 5^2014
tìm x thuộc Z
a) 1/3 + (-2)/5 + 1/6 + (-1)/5 < x < ( -3)/4 + 2/7 + (-1)/4 + 3/5 + 5/7
b) 5/17 + (-4)/9 + (-20)/31 + 12/17 + (-11)/31 < x/9 < (-3)/7 + 7/15 + 4/(-7) + 8/15 +2/3
Bài 6 : Tính giá trị các biểu thức .
a. A = -5/7 + 7/-5 + 4/7 + 7/4 .
b. B = 2/-5 + -3/7 + -7/10 + 3/-8 .
c. C = -5/7 + 2/-7 + 4/-9 + 4/9 .
d. D = ( 3 - 3/4 + 2/3 ) - ( 2 + 4/3 - 3/2 ) - ( 1 - 7/3 - 9/2 ) .