Resposta :
Olá, Isa Brasil.
[tex]a) \frac{2x^2+x-1}{x-\frac12}=\frac{2x^2+2x-x-1}{x-\frac12}=\frac{2x^2-x+2x-1}{x-\frac12}=\frac{2x(x-\frac12)+2(x-\frac12)}{x-\frac12}=\\\\\\ =\frac{2x(x-\frac12)}{x-\frac12}+\frac{2(x-\frac12)}{x-\frac12}=2x+2=2(x+1)[/tex]
[tex]b)\frac{(x+b)^2-b^2}{(-x-2b)x}=\frac{x^2+2bx+b^2-b^2}{-x^2-2bx}=\frac{x^2+2bx}{-(x^2+2bx)}=-1[/tex]