Question

Bài 1 : Giải các phương trình sau:

a) x³ -2x²-3x+4=0

d) x⁴-5x²-6=0

f) -x⁴-x²+2=0

Làm ơn giải giúp giùm ạ QwQ

Answer 1

a)\(x^3-2x^2-3x+4=0\)

\(\Leftrightarrow x^2\left(x-1\right)-x\left(x-1\right)-4\left(x-1\right)=0\)

\(\Leftrightarrow\left(x^2-x-4\right)\left(x-1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=\frac{1+\sqrt[]{17}}{2}\\x=\frac{1-\sqrt{17}}{2}\end{matrix}\right.\)

Answer 2

b)\(x^4-5x^2-6=0\)

\(\Leftrightarrow x^2\left(x^2-6\right)+x^2-6=0\)

\(\Leftrightarrow\left(x^2+1\right)\left(x^2-6\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x^2+1=0\\x^2-6=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\sqrt{6}\\x=-\sqrt{6}\end{matrix}\right.\)