I : PTĐTTNT

A= \(\left(x^2-6x\right)^2-2\left(x-3\right)^2-81\)

B=\(x^4+y^4+z^4-2x^2y^2-2y^2z^2-2x^2z^2\)

help me !!!

I : PTĐTTNT

4x^4+y^4

I : Cho tam giác ABC nhọn , đường cao AD . H là trực tâm

a) C/m : AD.BH=BD.CD

b) C/m: AD.DH\(\le\)\(\frac{BC^2}{4}\)

help me !!!

I : PTĐTTNT

\(\left(x^2-x-2\right)^2+\left(x-2\right)^2\)

help me