3x^1-n(xⁿ⁺¹+yⁿ⁺¹)- 3x^1-nyⁿ⁺¹=27

<=> 3x²+3x^1-n.yⁿ⁺¹-3x^1-nyⁿ⁺¹=27

<=> 3x²=27

<=> x²=9

<=>\(\orbr{\begin{cases}x=3\\x=-3\end{cases}}\)

3x^{1 - n}(x^{n + 1} + y^{n + 1}) - 3x^{1 - n}y^{n + 1} = 27

<=> 3x² = 27

<=> x² = 27 : 3

<=> x² = 9

<=> x² = 3²; -3²

=> x = 3; -3

3x^n-1(x^n-1+y^n-1)-3x^n-1.yⁿ⁺¹=27

<=>3x^n-1.x^n-1+3x^n-1.y^n-1-3x^n-1.yⁿ⁺¹=27

<=>(3x²)^n-1=27

mjk chj giải dc tới đây

\(3x^{n-1}\left(x^{n+1}+y^{n+1}\right)-3x^{n-1}.y^{n+1}=27.\)

\(3x^{n+1+n+1}+3x^{n-1}y^{n+1}-3x^{n-1}y^{n+1}=27\)

\(3x^{2n}=27\)

\(x^{2n}=9\)

\(x^{2n}=3^2\)

\(2n=2\)

\(n=1\)

a/ \(x^2+y^2=x^2+y^2+2xy-2xy =\left(x+y\right)^2-2xy\)

b/ mình không chắc nữa

bài 3

a/ \(9x^2-49=0 \Leftrightarrow x^2=\frac{49}{9} \Leftrightarrow\orbr{\begin{cases}x=\frac{7}{3}\\x=-\frac{7}{3}\end{cases}}\)

b/ \(\left(x+3\right)\left(x^2-3x+9\right)-x\left(x+1\right)\left(x-1\right)-27=0 \Leftrightarrow x^3+27-x\left(x^2-1\right)-27=0\)

\(\Leftrightarrow x^3-x^3+x=0\Leftrightarrow x=0\)

c/\(\left(x-1\right)\left(x+2\right)-x-2=0 \Leftrightarrow \left(x-1\right)\left(x+2\right)-\left(x+2\right)=0\)

\(\Leftrightarrow\left(x+2\right)\left(x-1\right)^2=0\Leftrightarrow\orbr{\begin{cases}x+2=0\\x-1=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=-2\\x=1\end{cases}}}\)

d/ \(x\left(3x+2\right)+\left(x+1\right)^2-\left(2x-5\right)\left(2x+5\right)=0\)

\(\Leftrightarrow3x^2+2x+x^2+2x+1-4x^2+25=0\)

\(\Leftrightarrow4x+25=0 \Leftrightarrow x=\frac{-25}{4}\)

e/ mình lười qá ko viết đề đâu 

\(\Leftrightarrow4x^2-7x-2-4x^2+4x+3=7\)

\(\Leftrightarrow-3x+1=7 \Leftrightarrow x=-2\)

có gì sai bn sửa lại nha 

a) \(=3x^{n-2}.x^{n+2}-3x^{n-2}.y^{n+2}+y^{n+2}.3x^{n-2}-y^{n+2}.y^{n-2}\)

    \(=3x^n-y^n\)

b) ; c) ; d) Tương tự nhé