3^x+3^x+2=812

3^x+3^x.3^2=812

3^x.(1+3^2)=812

3^x.10=812

3^x=812:10

3^x=812/10

=> x k có giá trị

     x thuộc tập hợp rỗng

a)  x + y = 10 ⇒ y = 10 − x ⇒ 3 x = 2 ( 10 − x ) ⇒ x = 4 ⇒ y = 6

b)  y − x = − 4 ⇒ y = x − 4 ⇒ x − 2 x − 4 + 3 = 8 12 ⇒ x − 2 x − 1 = 8 12 ⇒ 12 x − 24 = 8 x − 8 ⇒ x = 4 ⇒ y = 0

c)  x + 2 y = 12 ⇒ x = 12 − 2 y ⇒ 12 − 2 y 2 = y 5 ⇒ 60 − 10 y = 2 y ⇒ y = 5 ⇒ x = 2

a) x = 10,75               b) x = 0

812x5+812x7-812x2

=812x(5+7-2)

=812x10

=8120

   812 x 5 + 812 x 7 - 812 x 2

= 812 x ( 5 + 7 - 2 )

= 812 x  10

= 8120

Chúc bn hok tốt !

   812 x 5 + 812 x 7 - 812 x 2
= 812 x ( 5 + 7 - 2 )
= 812 x  10
= 8120

Đáp án:

$P=\pm 36$

Giải thích các bước giải:

Ta có:

x2+y2+z2=16xy−yz+zx=−10⇒(x2+y2+z2)−2.(xy−yz+zx)=16−2.(−10)⇔x2+y2+z2−2xy+2yz−2zx=36⇔(x2−2xy+y2)+z2+2yz−2zx=36⇔(x−y)2+2z(y−x)+z2=36⇔(x−y)2−2.(x−y).z+z2=36⇔(x−y−z)2=36⇔x−y−z=±6P=x3−y3−z3−3xyz=(x3−3x2y+3xy2−y3)−z3+3x2y−3xy2−3xyz=(x−y)3−z3+3x2y−3xy2−3xyz=[(x−y)−z].[(x−y)2+(x−y).z+z2]+3xy(x−y−z)=(x−y−z).(x2−2xy+y2+xz−yz+z2+3xy)=(x−y−z).(x2+y2+z2+xy−yz+zx)Trường hợp 1: x−y−z=6⇒P=6.(16+(−10))=36Trường hợp 2: x−y−z=−6⇒P=(−6).(16+(−10))=−36x2+y2+z2=16xy−yz+zx=−10⇒(x2+y2+z2)−2.(xy−yz+zx)=16−2.(−10)⇔x2+y2+z2−2xy+2yz−2zx=36⇔(x2−2xy+y2)+z2+2yz−2zx=36⇔(x−y)2+2z(y−x)+z2=36⇔(x−y)2−2.(x−y).z+z2=36⇔(x−y−z)2=36⇔x−y−z=±6P=x3−y3−z3−3xyz=(x3−3x2y+3xy2−y3)−z3+3x2y−3xy2−3xyz=(x−y)3−z3+3x2y−3xy2−3xyz=[(x−y)−z].[(x−y)2+(x−y).z+z2]+3xy(x−y−z)=(x−y−z).(x2−2xy+y2+xz−yz+z2+3xy)=(x−y−z).(x2+y2+z2+xy−yz+zx)Trường hợp 1: x−y−z=6⇒P=6.(16+(−10))=36Trường hợp 2: x−y−z=−6⇒P=(−6).(16+(−10))=−36

Vậy $P=\pm 36$.

MÌNH CHỈ BIẾT LÀM B7 THÔI NHA

P= 811^3+ 812^3+815^3+3.811.812.(-815)=  31694

K ĐÚNG HỘ TỚ NHA

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\(\left|x^3+x\right|-\left|9x^2+9\right|=0\)

\(\Leftrightarrow\left|x\left(x^2+1\right)\right|-9\left|x^2+1\right|=0\)

\(\Leftrightarrow\left(\left|x\right|-9\right)\left(x^2+1\right)=0\)

\(\Leftrightarrow\left|x\right|=9\left(x^2+1\ge1>0\right)\Leftrightarrow x=\pm9\)

Vậy ... 

\(\left|x^3+x\right|-\left|9x^2+9\right|=0\)

\(TH1:\left\{{}\begin{matrix}\left|x^3+x\right|=0\\\left|9x^2+9\right|=0\end{matrix}\right.\)

\(\text{Vì }9x^2\ge0\)

\(\Rightarrow9x^2+9\ge9\)

\(TH2:\left|x^3+x\right|=\left|9x^2+9\right|\)

\(\Rightarrow\left[{}\begin{matrix}x^3+x=9x^2-9\\x^3+x=9x^2+9\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x^3+x+9x^2+9=0\\x^3+x-9x^2-9=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x.\left(x^2+1\right)+9.\left(x^2+1\right)=0\\x.\left(x^2+1\right)-9.\left(x^2+1\right)=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-9\\x=9\end{matrix}\right.\)

=>|x^3+x|=|9x^2+9|

=>x^3+x=9x^2+9 hoặc x^3+x=-9x^2-9

=>x^3-9x^2+x-9=0 hoặc x^3+9x^2+x+9=0

=>x+9=0 hoặc (x-9)(x^2+1)=0

=>x=9 hoặc x=-9

Ta có: \(x^3+6x^2+9x=0\)

\(\Leftrightarrow x\left(x+3\right)^2=0\)

hay \(x\in\left\{0;-3\right\}\)

x³+6x²+9x=0

⇒x(x²+6x+9)=0

⇒x(x+3)²=0

⇒\(\left[{}\begin{matrix}x=0\\\left(x+3\right)^2=0\end{matrix}\right.\)

⇒\(\left[{}\begin{matrix}x=0\\x+3=0\end{matrix}\right.\)

⇒\(\left[{}\begin{matrix}x=0\\x=-3\end{matrix}\right.\)

\(pt< =>x\left(x^2+6x+9\right)=0< =>x\left(x+3\right)^2=0\)

\(=>\left[{}\begin{matrix}x=0\\x=-3\end{matrix}\right.\)