\(\left(x^2-4\right)\left(x^2+4\right)=0\)

Do \(x^2+4>0\forall x\)

nên \(x^2-4=0\)

\(\Leftrightarrow x^2=4\)

\(\Leftrightarrow x=\pm2\)

(x² - 4 ) . ( x² + 4 ) = 0

\(\Rightarrow\hept{\begin{cases}x^2-4=0\\x^2+4=0\end{cases}\Rightarrow\hept{\begin{cases}x^2=4\\x^2=-4\left(l\right)\end{cases}}}\)

\(\Leftrightarrow x=\pm2\)

-2 ( 2x³ + 1 ) + 87 = -23

-4x³ - 2 + 87 = -23

-4x³ + 85 = -23

-4x³ = -108

x³ = 27 = 3³

x = 3

Vậy....

\(-2\left(2x^3+1\right)+87=-23\)

\(\Rightarrow2x^3+1=\left(-23-87\right):-2=55\)

\(\Rightarrow2x^3=54\)

\(\Rightarrow x^3=27\Leftrightarrow x=3\)

\(a,\)\(9-25=\left(7-x\right)-\left(25+7\right)\)

\(-16=\left(7-x\right)-32\)

\(7-x=-16+32\)

\(7-x=16\)

\(x=7-16=-9\)

\(b,-7624+\left(1543+7624\right)-x=25\)

\(-7624+9167-x=25\)

\(1543-x=25\)

\(x=1543-25\)

\(x=1518\)

\(c,\left(27-514\right)-\left(486-73\right)+x=7\)

\(-487-413+x=7\)

\(-900+x=7\)

\(x=7+900\)

\(x=907\)

\(A=2+2^3+...+2^8\)

\(2A=2^2+2^4+...+2^9\)

\(2A-A=\left(2^2+2^4+...+2^9\right)-\left(2+2^3+...+2^8\right)\)

\(A=2^2+2^9-2-2^3\)

\(A=4+512-2-8\)

\(A=506\)

\(A=2+2^2+2^3+...+2^8\)

\(2A=2^2+2^3+...+2^9\)

\(\Rightarrow2A-A=2^9-2\)

\(\Rightarrow A=2^9+2\)

=2016 nha

=26/15;-26/15 nha bạn