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a) \(2^x=8.64=2^3.2^6=2^9\Rightarrow x=9\)
b) \(3.2^x=48\Rightarrow2^x=16=2^4\Rightarrow x=4\)
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a: =>2x=-18+5=-13
=>x=-13/2
b: =>3^x-1=81
=>x-1=4
=>x=5
c: =>4(5-x)=24
=>5-x=6
=>x=-1
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a) \(\left(\frac{2x}{3}-3\right)\div\left(-10\right)=\frac{2}{5}\)
\(\Rightarrow\left(\frac{2x}{3}-\frac{9}{3}\right).-\frac{1}{10}=\frac{2}{5}\)
\(\Rightarrow\frac{2x-9}{3}.-\frac{1}{10}=\frac{2}{5}\)
\(\Rightarrow\frac{9-2x}{30}=\frac{2}{5}\Rightarrow\left(9-2x\right).5=60\)
\(\Rightarrow45-10x=60\Rightarrow-10x=15\Rightarrow x=-\frac{15}{10}=-1,5\)
b)\(\left(x+5\right)^3=64\)
\(\Rightarrow\left(x+5\right)^3=4^3\)
\(\Rightarrow x+5=4\Rightarrow x=-1\)
A, 2x/3-3=-4
2x/3=-1
2x=-3
X=-3/2
B,(x+5)^3=4^3
=> x+5=4
X=-1
k nha
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Q=1.2.(3-1)+2.3.(4-1)+3.4.(5-1)+...+19.20.(21-1)=
=(1.2.3+2.3.4+3.4.5+...+19.20.21)-(1.2+2.3+3.4+...+19.20)
Đặt
A=1.2.3+2.3.4+3.4.5+...+19.20.21
4A=1.2.3.4+2.3.4.4+3.4.5.4+...+19.20.21.4=
=1.2.3.4+2.3.4(5-1)+3.4.5.(6-2)+...+19.20.21.(22-18)=
=1.2.3.4-1.2.3.4+2.3.4.5-2.3.4.5+3.4.5.6-...-18.19.20.21+19.20.21.22=
=19.20.21.22
\(A=\dfrac{19.20.21.22}{4}=5.19.21.22\)
Đặt
B=1.2+2.3+3.4+...+19.20
3B=1.2.3+2.3.3+3.4.3+...+19.20.3=
=1.2.3+2.3.(4-1)+3.4.(5-2)+...+19.20.(21-18)=
=1.2.3-1.2.3+2.3.4-2.3.4+3.4.5-...-18.19.20+19.20.21=
=19.20.21
\(B=\dfrac{19.20.21}{3}=7.19.20\)
Q=A-B
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a, \(\left(2x+1\right)^4=225\)
đề bài sai
bởi vì ko có số nào mà ^4 lên đc kết quả là 225
b, \(\left(3x-1\right)^2=64\)
Ta có : \(8^2=64\)
Vậy suy ra : 3x - 1 = 8
3x = 8 + 1
3x = 9
x = 9 : 3
x = 3