4/(y-x)(x-z)+3/(y-x)(y-z)+3/(y-z)(x-z)

\(\frac{7}{15}+\frac{1}{3}=\frac{4}{5}\)

A= 5/a+1-10/a-(a^2+1)-15b/a^3b+b

Chứng minh đẳng thức:

a, (x^2-2x/2x^2+8-2x^2/8-4x+2x^2-x^3)(1-1/x-2/x^2)=x+1/2x

b, [2/3x-2/x+1(x+1/3x-x-1)]:x-1/x=2x/x-1

c, [2/(x+1)^3(1/x+1)+1/x^2+2x+1(1/x^2+1)]:x-1/x^3=x/x-1

3(x-2)²+9(x-1)=3(x²⁺x-3)