Question

tìm nghiệm của đa thức sau

a,\(3x-\dfrac{2}{5}\)

b,\(\left(x-3\right)\).\(\left(2x+8\right)\)

c, \(3.x^2\)-\(x\)-\(4\)

mn giúp mik vs ạ , mik c.on trc ạ

 

 

Answer 1

a)\(3x-\dfrac{2}{5}=0=>3x=\dfrac{2}{5}=>x=\dfrac{2}{15}\)

b)\(\left(x-3\right)\left(2x+8\right)=0=>\left[{}\begin{matrix}x-3=0\\2x=-8\end{matrix}\right.=>\left[{}\begin{matrix}x=3\\x=-4\end{matrix}\right.\)

c)\(3x^2-x-4=0=>3x^2+3x-4x-4=0=>\left(3x-4\right)\left(x+1\right)=0\)

\(=>\left[{}\begin{matrix}3x=4\\x+1=0\end{matrix}\right.=>\left[{}\begin{matrix}x=\dfrac{3}{4}\\x=-1\end{matrix}\right.\)