\(B=\frac{2x}{y+z+t}-\frac{3y}{x+z+t}+\frac{4z}{x+y+t}-\frac{5t}{x+y+z}\)
\(B=\frac{2x}{-x}-\frac{3y}{-y}+\frac{4z}{-z}-\frac{5t}{-t}\)
\(B=-2+3-4+5=2\)
\(B=\frac{2x}{x+y+z+t-x}-\frac{3y}{x+y+z+t-y}+\frac{4z}{y+z+t+x-z}-\frac{5t}{x+y+z+t-t}\)
Thay x+y+z+t =0.Ta có
\(B=\frac{2x}{-x}-\frac{3y}{-y}+\frac{4z}{-z}-\frac{5t}{-t}=-2+3-4+5\)
B=2