Tìm tất cả số nguyên dương n sao cho : \(T=2^n+3^n+4^n\)là số chính phương
( Có vẻ như câu này khó đấy ! )
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Số số hạng là : \(\left(28,16-8,21\right):\left(9,26-8,21\right)+1=20\)
Tổng = \(\left(28,61+8,21\right)x20:2=368,2\)
Đấy là làm theo công thức đấy
A= 32 x 53 - 31
A= 1696 - 31
A= 1665
k cho mình nhaaaa
Kb đi nè :333
+) \(2x\left(x-4\right)-x\left(2x+3\right)+22=0\)
\(\Leftrightarrow2x^2-8x-2x^2-3x+22=0\)
\(\Leftrightarrow-11x+22=0\)
\(\Leftrightarrow-11\left(x-2\right)=0\)
\(\Leftrightarrow x-2=0\Leftrightarrow x=2\)
+) \(\left(2x+3\right)\left(3x+2\right)+2\left(1-3x\right)\left(x+\frac{1}{2}\right)=1\)
\(\Leftrightarrow6x^2+4x+9x+6+\left(2-6x\right)\left(x+\frac{1}{2}\right)=1\)
\(\Leftrightarrow6x^2+13x+6+2x+1-6x^2-3x=1\)
\(\Leftrightarrow12x+7=1\)
\(\Leftrightarrow x=\frac{-1}{2}\)
2x( x - 4 ) - x( 2x + 3 ) + 22 = 0
<=> 2x2 - 8x - 2x2 - 3x + 22 = 0
<=> -11x + 22 = 0
<=> -11x = -22
<=> x = 2
( 2x + 3 )( 3x + 2 ) + 2( 1 - 3x )( x + 1/2 ) = 1
<=> 6x2 + 13x + 6 + 2( -3x2 - 1/2x + 1/2 ) = 1
<=> 6x2 + 13x + 6 - 6x2 - x + 1 = 1
<=> 12x + 7 = 1
<=> 12x = -6
<=> x = -6/12 = -1/2
\(A=\left(x+y\right)^2+\left(x-y\right)^2-2\left(x^2y^2\right)\)
\(A=x^2+2xy+y^2+x^2-2xy+y^2-2x^2y^2\)
\(A=2x^2+2y^2-2x^2y^2\)
\(A=2\left(x^2-x^2y^2+y^2\right)\)
A = ( x + y )2 + ( x - y )2 - 2( x2y2 )
A = x2 + 2xy + y2 + x2 - 2xy + y2 - 2x2y2
A = 2x2 + 2y2 - 2x2y2
A = 2( x2 + y2 - x2y2 )
a) \(12^{10}:3^{10}=\left(12:3\right)^{10}=4^{10}\)
b) \(4^5.3^{10}=4^5.3^{2.5}=4^5.\left(3^2\right)^5=4^5.9^5=\left(4.9\right)^5=36^5\)
c) \(9^{10}:27^4=\left(3^2\right)^{10}:\left(3^3\right)^4=3^{2.10}:3^{3.4}=3^{20}:3^{12}=3^8\)
d) \(15^8:9^4=15^8:\left(3^2\right)^4=15^8:3^8=\left(15:3\right)^8=5^8\)
1.John's results were good.Fred's results were very poor.Fred's results were(bad) worse than
2.This exercise is not difficult.It's (easy) easier than
3.The weather is not good today-it's raining.I hope the weather will be (good) better.
4.People are not friendly in big cities. They are usually(friendly) more friendly
5. In the government of a country, the President is ( important) the most important
15. John's results were bad. Fred's results were very poor. Fred's results were worse.
16. This exercise is not difficult. It's easy.
17. The weather is not good today - It's raining. I hope the weather will be better.
18. People are not very friendly in big cities. They are usually unfriendly.
19. In the government of a country, the President is important.
1/2-(2/3×x-1/3)=2/3
(2/3×x-1/3)=1/2-1/3
(2/3×x-1/3)=1/6
2/3×x=1/6+1/3
2/3×x=1/2
x=1/2:2/3
x=3/4
vậy x=3/4
3/x+5=15%
3/x+5=3/20
3/x=3/20-5
3/x=-97/20
3×20=x×-97
60=x×-97
x×-97=60
x=60:-97
x=-60/97
vậy x=-60/97
Ta có:\(\frac{1}{2}-\left(\frac{2}{3}\times x-\frac{1}{3}\right)=\frac{2}{3}\Rightarrow\frac{2}{3}\times x-\frac{1}{3}=\frac{1}{2}-\frac{2}{3}\)
\(\Rightarrow\frac{2}{3}\times x-\frac{1}{3}=\frac{-1}{6}\)
\(\Rightarrow\frac{2}{3}\times x=\frac{-1}{6}+\frac{1}{3}\Rightarrow\frac{2}{3}\times x=\frac{1}{6}\Rightarrow x=\frac{1}{6}:\frac{2}{3}=\frac{1}{4}\)
Vậy x=1/4
Ta có:\(\frac{3}{x}+5=15\%\Rightarrow\frac{3}{x}=\frac{3}{20}-5\Rightarrow\frac{3}{x}=\frac{-97}{20}\Rightarrow x=\frac{3}{\frac{-97}{20}}=\frac{-60}{97}\)
Vậy x=-60/97
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