Sai đề thì phải

\(\Rightarrow5^y-2^x=624\)

Vì \(5^y\) lẻ, 624 chẵn nên \(2^x\) lẻ

Do đó \(x=0\)

\(\Rightarrow5^y-1=624\\ \Rightarrow5^y=625=5^4\\ \Rightarrow y=4\)

Vậy \(\left(x;y\right)=\left(0;4\right)\)

\(x^4-2x^2-100x-624=0\\ \Rightarrow\left(x^4+4x^3\right)-\left(4x^3+16x^2\right)+\left(14x^2+56x\right)-\left(156x-624\right)=0\\ \Rightarrow x^3\left(x+4\right)-4x^2\left(x+4\right)+14x\left(x+4\right)-156\left(x+4\right)=0\\ \Rightarrow\left(x^3-4x^2+14x-156\right)\left(x+4\right)=0\\ \Rightarrow\left[\left(x^3-6x^2\right)+\left(2x^2-12x\right)+\left(26x-156\right)\right]\left(x+4\right)=0\\ \Rightarrow\left[x^2\left(x-6\right)+2x\left(x-6\right)+26\left(x-6\right)\right]\left(x+4\right)=0\)

\(\Rightarrow\left(x^2+2x+26\right)\left(x-6\right)\left(x+4\right)=0\\ \Rightarrow\left[{}\begin{matrix}\left(x+1\right)^2+25=0\left(vô.lí\right)\\x=6\\x=-4\end{matrix}\right.\)

Vậy pt có tập nghiệm \(S=\left\{-4;6\right\}\)

Giúp mình với mấy bạn !!!!

Mình cảm ơn trước 

a: \(C=2\left(x^2+\dfrac{5}{2}x-\dfrac{1}{2}\right)\)

\(=2\left(x^2+2\cdot x\cdot\dfrac{5}{4}+\dfrac{25}{16}-\dfrac{33}{16}\right)\)

\(=2\left(x+\dfrac{5}{4}\right)^2-\dfrac{33}{8}>=-\dfrac{33}{8}\)

Dấu '=' xảy ra khi x=-5/4

b: \(=x^2+4x+4+y^2-6y+9-6\)

\(=\left(x+2\right)^2+\left(y-3\right)^2-6>=-6\)

Dấu '=' xảy ra khi x=-2 và y=3

giúp mình nhé