Toán Tìm x : (5-2x)^2-16=16 Làm giúp mình với ^ ^ Cần gấp 21/09/2021 By Gabriella Tìm x : (5-2x)^2-16=16 Làm giúp mình với ^ ^ Cần gấp
`(5-2x)^2-16=16` `<=>(5-2x)^2-16-16=0` `<=>(5-2x)^2-32=0` `<=>(5-2x)^2-(4\sqrt{2})^2=0` `<=>(5-2x-4\sqrt{2})(5-2x+4\sqrt{2})=0` `<=>` \(\left[ \begin{array}{l}5-2x-4\sqrt{2}=0\\5-2x+4\sqrt{2}=0\end{array} \right.\)`<=>` \(\left[ \begin{array}{l}-2x=4\sqrt{2}-5\\-2x=-4\sqrt{2}-5\end{array} \right.\) `<=>`\(\left[ \begin{array}{l}x=\dfrac{5-4\sqrt{2}}{2}\\x=\dfrac{5+4\sqrt{2}}{2}\end{array} \right.\) Vậy phương trình trên có nghiệm `S={\frac{5-4\sqrt{2}}{2};\frac{5+4\sqrt{2}}{2}}` Trả lời
Đáp án: ( 5 – 2$x_{}$ )² – 16 = 16 ⇔ ( 5 – 2$x_{}$ )² – 16 – 16 = 0 ⇔ ( 5 – 2$x_{}$ )² – 32 = 0 ⇔ ( 5 – 2$x_{}$ )² – ( 4√2 )² = 0 ⇔ ( 5 – 2$x_{}$ + 4√2 ) × ( 5 – 2$x_{}$ – 4√2 ) = 0 ⇔\(\left[ \begin{array}{l}5 – 2x + 4√2 = 0\\5 – 2x – 4√2 = 0\end{array} \right.\) ⇔\(\left[ \begin{array}{l} – 2x + 4√2 = -5\\ – 2x – 4√2 = -5\end{array} \right.\) ⇔\(\left[ \begin{array}{l} – 2x = -5 – 4√2 \\ – 2x = -5 + 4√2\end{array} \right.\) ⇔\(\left[ \begin{array}{l} x = \frac{- 5 – 4√2}{-2} \\x =\frac{- 5 + 4√2}{-2}\end{array} \right.\) ⇔\(\left[ \begin{array}{l} x = \frac{ 5 + 4√2}{2} \\x = \frac{5 – 4√2}{2}\end{array} \right.\) Giải thích các bước giải: Trả lời
`(5-2x)^2-16=16`
`<=>(5-2x)^2-16-16=0`
`<=>(5-2x)^2-32=0`
`<=>(5-2x)^2-(4\sqrt{2})^2=0`
`<=>(5-2x-4\sqrt{2})(5-2x+4\sqrt{2})=0`
`<=>` \(\left[ \begin{array}{l}5-2x-4\sqrt{2}=0\\5-2x+4\sqrt{2}=0\end{array} \right.\)`<=>` \(\left[ \begin{array}{l}-2x=4\sqrt{2}-5\\-2x=-4\sqrt{2}-5\end{array} \right.\) `<=>`\(\left[ \begin{array}{l}x=\dfrac{5-4\sqrt{2}}{2}\\x=\dfrac{5+4\sqrt{2}}{2}\end{array} \right.\)
Vậy phương trình trên có nghiệm `S={\frac{5-4\sqrt{2}}{2};\frac{5+4\sqrt{2}}{2}}`
Đáp án:
( 5 – 2$x_{}$ )² – 16 = 16
⇔ ( 5 – 2$x_{}$ )² – 16 – 16 = 0
⇔ ( 5 – 2$x_{}$ )² – 32 = 0
⇔ ( 5 – 2$x_{}$ )² – ( 4√2 )² = 0
⇔ ( 5 – 2$x_{}$ + 4√2 ) × ( 5 – 2$x_{}$ – 4√2 ) = 0
⇔\(\left[ \begin{array}{l}5 – 2x + 4√2 = 0\\5 – 2x – 4√2 = 0\end{array} \right.\)
⇔\(\left[ \begin{array}{l} – 2x + 4√2 = -5\\ – 2x – 4√2 = -5\end{array} \right.\)
⇔\(\left[ \begin{array}{l} – 2x = -5 – 4√2 \\ – 2x = -5 + 4√2\end{array} \right.\)
⇔\(\left[ \begin{array}{l} x = \frac{- 5 – 4√2}{-2} \\x =\frac{- 5 + 4√2}{-2}\end{array} \right.\)
⇔\(\left[ \begin{array}{l} x = \frac{ 5 + 4√2}{2} \\x = \frac{5 – 4√2}{2}\end{array} \right.\)
Giải thích các bước giải: