Xét: \(4x-1=0\Leftrightarrow x=\dfrac{1}{4}\); \(x+2=0\Leftrightarrow x=-2\); \(3x-5=0\Leftrightarrow x=\dfrac{5}{3}\); \(-2x+7=0\Leftrightarrow x=\dfrac{7}{2}\). TenAnh1 TenAnh1 B = (11.24, -6.26) B = (11.24, -6.26) B = (11.24, -6.26) C = (-0.38, -6.9) C = (-0.38, -6.9) C = (-0.38, -6.9) D = (14.98, -6.9) D = (14.98, -6.9) D = (14.98, -6.9) Vậy: \(f\left(x\right)=0\) khi \(x=\left\{-2;-\dfrac{1}{4};\dfrac{5}{3};\dfrac{7}{2}\right\}\). \(f\left(x\right)>0\) khi \(\left(-2;-\dfrac{1}{4}\right)\cup\left(\dfrac{5}{3};\dfrac{7}{2}\right)\). \(f\left(x\right)< 0\) khi \(\left(-\infty;-2\right)\cup\left(-\dfrac{1}{4};\dfrac{5}{3}\right)\cup\left(\dfrac{7}{2};+\infty\right)\).