Đáp án:
tham khảo
Giải thích các bước giải:
`B(x)=3(2x-1)-2(x+1)`
cho `B(x)=0`
`<=>3(2x-1)-2(x+1)=0`
`<=>6x-3-2x-2=0`
`<=>6x-2x-5=0`
`<=>4x=5`
`<=>x=5/4`
$\\$
`C(x)=(2x^2-8)(-x^2+1)`
cho `C(x)=0`
`<=>(2x^2-8)(-x^2+1)=0`
`<=>-2(x^2-4)(x^2-1)=0`
`<=>(x^2-4)(x^2-1)=0`
`<=>` \(\left[ \begin{array}{l}x^2-4=0\\x^2-1=0\end{array} \right.\) `<=>` \(\left[ \begin{array}{l}x^2=4\\x^2=1\end{array} \right.\) `<=>` \(\left[ \begin{array}{l}x=2\\x=-2\\x=1\\x=-1\end{array} \right.\)
$\\$
`D(x)=3x-x^3`
cho `D(x)=0`
`<=>3x-x^3=0`
`<=>x(3-x^2)=0`
`<=>` \(\left[ \begin{array}{l}x=0\\x=3-x^2=0\end{array} \right.\) `<=>` \(\left[ \begin{array}{l}x=0\\x^2=3\end{array} \right.\) `<=>` \(\left[ \begin{array}{l}x=0\\x=\sqrt3\\x=-\sqrt3\end{array} \right.\)
$\\$
`E(x)=2x^3+4x`
cho `E(x)=0`
`<=>2x^3+4x=0`
`<=>2x(x^2+2)=0`
`<=>` \(\left[ \begin{array}{l}2x=0\\x^2+2=0\end{array} \right.\) `<=>` \(\left[ \begin{array}{l}x=0\\x^2=-2\end{array} \right.\) `<=>` `x=0`
