phata1pvd

Tính $\lim_{x \to +\infty} \left ( \tan {\dfrac{\pi x}{2x+1}} -1 \right)^{\dfrac{1}{x^2}} $

Giải HPT:$\left\{\begin{matrix}(x+y)\sqrt{2xy+5}=4xy-3y+1 & \\ (x+2y)\sqrt{2xy+5}=6xy+x-7y-6&\end{matrix}\right.$

Giải PT: $x^{3}+4x=4x\sqrt{x^{3}+1}$