Question

 

Answer 1

a: \(5x^2-9x-2=0\)

=>\(5x^2-10x+x-2=0\)

=>5x(x-2)+(x-2)=0

=>(x-2)(5x+1)=0

=>\(\left[{}\begin{matrix}x-2=0\\5x+1=0\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}x=2\\x=-\dfrac{1}{5}\end{matrix}\right.\)

c: \(-2x^3+x^2-3=0\)

=>\(-2x^3-2x^2+3x^2-3=0\)

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

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

mà \(-2x^2+3x-3\ne0\forall x\)

nên x+1=0

=>x=-1