Đáp án:
`a)` `x=5/6`
`b)` `x=+-2/5`
`c)` `x=-2/3`
`d)` \(\left[ \begin{array}{l}x=0\\x=±\frac{\sqrt{2}}{4}\end{array} \right.\)
`e)` `x=+-2/3`
`f)` \(\left[ \begin{array}{l}x=0\\x=\dfrac{3}{2} \\x=1\end{array} \right.\)
`g)` \(\left[ \begin{array}{l}x=2\\x=6\end{array} \right.\)
`h)` \(\left[ \begin{array}{l}x=0\\x=2\end{array} \right.\)
`i)` \(\left[ \begin{array}{l}x=1\\x=-5\end{array} \right.\)
Giải thích các bước giải:
`a)` Cho `A=-2/3x-5/9=0`
`->` `x=-5/6`
Vậy `x=5/6`
`b)` Cho `B=x^2-4/25=0`
`->` `x^2=4/25`
`->` `x=+-2/5`
Vậy `x=+-2/5`
`c)` Cho `C=1/2x^3+4/27=0`
`->` `1/2x^3=-4/27`
`->` `x^3=-8/27`
`->` `x=-2/3`
Vậy `x=-2/3`
`d)` Cho `D=x^3-1/8x=0`
`->` `x(x^2-1/8)=0`
`->`\(\left[ \begin{array}{l}x=0\\x^2-\dfrac{1}{8}=0\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=0\\x^2=\dfrac{1}{8}\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=0\\x=±\frac{\sqrt{2}}{4}\end{array} \right.\)
Vậy \(\left[ \begin{array}{l}x=0\\x=±\frac{\sqrt{2}}{4}\end{array} \right.\)
`e)` Cho `E=x^4-16/81=0`
`->` `x^4=16/81`
`->` `x=+-2/3`
Vậy `x=+-2/3`
`f)` Cho `F=-x(-2x+3)(1-x^3)=0`
`->` \(\left[ \begin{array}{l}-x=0\\-2x+3=0\\1-x^3=0\end{array} \right.\)
`->`\(\left[ \begin{array}{l}x=0\\x=\dfrac{3}{2} \\x=1\end{array} \right.\)
Vậy \(\left[ \begin{array}{l}x=0\\x=\dfrac{3}{2} \\x=1\end{array} \right.\)
`g)` Có `G=2(2-x)+1/2(x-2)^2=2(2-x)+1/2(2-x)^2`
`=(2-x)[2+1/2(2-x)]`
`=(2-x)(3-1/2x)`
Cho `G=(2-x)(3-1/2x)=0`
`->` \(\left[ \begin{array}{l}2-x=0\\3-\dfrac{1}{2}x=0\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=2\\x=6\end{array} \right.\)
Vậy \(\left[ \begin{array}{l}x=2\\x=6\end{array} \right.\)
`h)` Cho `H=x^100-8x^97=0`
`->` `x^97.(x^3-8)=0`
`->`\(\left[ \begin{array}{l}x=0\\x^3-8=0\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=0\\x=2\end{array} \right.\)
Vậy \(\left[ \begin{array}{l}x=0\\x=2\end{array} \right.\)
`i)` Cho `I=(x-1)(x+5)=0`
`->` \(\left[ \begin{array}{l}x-1=0\\x+5=0\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=1\\x=-5\end{array} \right.\)
Vậy \(\left[ \begin{array}{l}x=1\\x=-5\end{array} \right.\)
