Question

nghiem x>0 cua phuong trinh: x+can3+3x^2-9=0

Answer 1

Theo đề: nghiem x>0 cua phuong trinh: x+can3+3x^2-9=0

<=> x+căn3+3(x^2-3)=0

<=>x+căn3+3(x+canw3)(x-căn 3)=0

<=>(x+can3)(1+3x-can3)=0

<=>x= - căn 3 hoặc x=(-1+căn 3)/3

Answer 2

Ta co: x>0

\(x+\sqrt{3}+3x^2-9=0\)

\(<=>x+\sqrt{3}+3\left(x+\sqrt{3}\right)\left(x-\sqrt{3}\right)=0\)

\(<=>\left(x+\sqrt{3}\right)\left(x-\sqrt{3}\right)=0\)

\(<=>x=-\sqrt{3};\sqrt{3}\)