tim x
8B-7=-7^x biet B=7-7^2+7^3-....-7^120
NT
Những câu hỏi liên quan
tim x biet: a) |x+2| - 6x=7 b) |x-3|+|x+2|=7
Tong cua 3 so la 120.Tim 3 so do,biet so thu nhat it hon so thu 2 7 don vi,so thu 2 it hon so thu 3 7 don vi
nhanh giup em
Cho bieu thuc
\(a=1+7+7^2+7^3+...+7^{100}\)
a) Tinh a
b) Tim x biet \(6a+1=7^x\)
c) Tim du trong phep chia a cho 8
c)\(a=1+7+7^2+...+7^{100}\)
\(a=\left(1+7\right)+\left(7^2+7^3\right)+...+\left(7^{99}+7^{100}\right)\)
\(a=8+7^2\left(1+7\right)+...+7^{99}\left(1+7\right)\)
\(a=8+7^2.8+...+7^{99}.8\)
\(a=8\left(1+7^2+...+7^{99}\right)\) chia hết cho 8
=> a chia 8 dư 0
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a)\(a=\left(1+7+7^2+...+7^{100}\right)\)
=>\(7a=7\left(1+7+7^2+...+7^{100}\right)=7+7^2+7^3+...+7^{101}\)
=>\(7a-a=\left(7+7^2+7^3+...+7^{101}\right)\)\(-\left(1+7+7^2+...+7^{100}\right)\)
=>\(6a=7^{101}-1\Rightarrow a=\frac{7^{101}-1}{6}\)
b)\(6a+1=7^x\Rightarrow6.\frac{7^{101}-1}{6}+1=7^x\Rightarrow7^{101}-1+1=7^x\Rightarrow7^{101}=7^x\)=>x=101
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tim x biet :
-x-2/3=-6/7
4/7-x=1/3
-x-2/3=-6/7
=>-x=-6/7+(-2/3)
=>-x=-32/21
=>x=32/21
4/7-x=1/3
=>x=4/7-1/3
=>x=5/21
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-x-2/3=-6/7
=>-x=-6/7+(-2/3)
=>-x=-32/21
=>x=32/21
4/7-x=1/3
=>x=4/7-1/3
=>x=5/21
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tim x biet:
a)|x|=5
b)|x|+3=7
c)\x|-2=3
d)|2x-4|+7=10
a)x=5
b)x=7-3
x=4
c)x=3+2
x=5
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tim x biet : a,-12/21×x + 3/7=-4/3, b, 2x +-3^2=5/4 , c, 75% x- 2/5=3/10, d, (3x-2)×(x+7)
tim x, biet 2/7^6x-7=1
tim x biet
1)0,(31)+x=0,(7)
2)0,(4)nhan x=3/7
Tim cac so x,y,z biet x/y=9/7; y/2=7/3 va x-y+z=-15