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1−5−9+13+17−21−25+...−393+397+401
=(1−5−9+13)+(17−21−25+29)+...+(385−389−393+397)+401
=0+0+...+0+401=401
\(1-5-9+13+17-21-25+...-393+397+401\)
\(=\left(1-5-9+13\right)+\left(17-21-25+29\right)+...+\left(385-389-393+397\right)+401\)
\(=0+0+...+0+401=401\)
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393-19.(x-7)=169:13
=> 393-19.(x-7)=13
=> 19(x-7)=393-13
=> 19(x-7)=380
=> x-7=380:19
=> x-7=20
=> x= 20+7
=> x=27
Vậy x = 27
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\(390-\left(x-7\right)=169:3\)
\(\Rightarrow390-\left(x-7\right)=\dfrac{169}{3}\)
\(\Rightarrow x-7=390-\dfrac{169}{3}\)
\(\Rightarrow x-7=\dfrac{1001}{3}\)
\(\Rightarrow x=\dfrac{1001}{3}+7\)
\(\Rightarrow x=\dfrac{1022}{3}\)
390-(X-7)=169:3
390 - (X-7)= 169/3
X - 7 = 390 - 169/3
X - 7 = 1001/3
X= 1001/3 + 7
X= 1022/3
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-(-390)+(-132)-311+1
=390+(-132)-311+1
=258-311+1
=-53+1
=-52
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\(5.3^{x+1}-4.3^{x-2}=393\)
\(5.3^x.3-4.3^x:9=393\)
\(3^x\left(15-\frac{4}{9}\right)=393\)
\(3^x\frac{131}{9}=393\)
\(3^x=27\)
\(3^x=3^3\)
\(\Rightarrow x=3\)
(393+390) :(317.373)
= ( 3 mũ 93 + 3 mũ 90 ) : 3 mũ 90
= 3 mũ 93