b)
\frac{4}{2x^2+x} - \frac{6x}{2x+1} = 1
\frac{4}{x(2x+1)} - \frac{6x}{2x+1}=1 |* x(2x + 1)
4-x*6x=x(2x+1)
4-6x^2=2x^2+x
4-6x^2-2x-x=0
-8x^2-x+4=0
a=-8 , b=-1 , c=4
\Delta=b^2-4ac=1+32*4=1+128=129
\sqrt\Delta=\sqrt{129}
x_1=\frac{-b-\sqrt\Delta}{2a}=\frac{1-\sqrt{129}}{-16}=\frac{-(\sqrt{129}-1)}{-16}=\frac{\sqrt{129}-1}{16}
x_2=\frac{-b+\sqrt\Delta}{2a}=\frac{1+\sqrt{129}}{-16}=\frac{-1-\sqrt{129}}{16}