Bài toán 3 : Tìm x biết.
a) 4x(x + 1) = 8(x + 1)
g) 5x(x – 2000) – x + 2000 = 0
b) x(x – 1) – 2(1 – x) = 0
h) x – 4x = 0
c) 2x(x – 2) – (2 – x) = 0
k) (1 – x) – 1 + x = 0
d) (x – 3) + 3 – x = 0
m) x + 6x = 0
Bài toán 3 : Tìm x biết.
a) 4x(x + 1) = 8(x + 1)
g) 5x(x – 2000) – x + 2000 = 0
b) x(x – 1) – 2(1 – x) = 0
h) x – 4x = 0
c) 2x(x – 2) – (2 – x) = 0
k) (1 – x) – 1 + x = 0
d) (x – 3) + 3 – x = 0
m) x + 6x = 0
`a, 4x(x+1)=8(x+1)`
`⇔4x(x+1)-8(x+1)=0`
`⇔(x+1)(4x-8)=0`
`<=>x=-1` hoặc `x=2`
`b, x(x-1)-2(1-x)=0`
`⇔ x(x-1)+2(x-1)=0`
`⇔ (x+2)(x-1)=0`
`⇔` `x=-2` hoặc `x=1`
`c, 2x(x-2)-(2-x)=0` `⇔ 2x(x-2)+(x-2)=0` `⇔ (2x+1)(x-2)=0` `⇔x=-1/2` hoặc `x=2`
`d, (x-3) +3-x=0` `⇔x-3 + 3-x=0` `⇔0=0` `=>` Pt vô số no
`g, 5x(x-2000) – x+2000=0` `⇔5x(x-2000)-(x-2000)=0` `⇔(5x-1)(x-2000)=0` `⇔` `x=-1/5` hoặc `x=2000`
`h, x – 4x = 0` `⇔ x = 0`
`k, (1-x) – 1+x=0` `⇔1-x-1+x=0` `⇔0=0` `⇔` Pt vô số no.
`m, x +6x = 0` `⇔ x=0`
Vậy …………………………………
`a, 4x(x+1)=8(x+1)`
`⇔4x(x+1)-8(x+1)=0`
`⇔(x+1)(4x-8)=0`
`⇔` \(\left[ \begin{array}{l}x+1=0\\4x-8=0\end{array} \right.\) `⇔` \(\left[ \begin{array}{l}x=-1\\x=2\end{array} \right.\)
`b, x(x-1)-2(1-x)=0`
`⇔ x(x-1)+2(x-1)=0`
`⇔ (x+2)(x-1)=0`
`⇔` \(\left[ \begin{array}{l}x+2=0\\x-1=0\end{array} \right.\) `⇔` \(\left[ \begin{array}{l}x=-2\\x=1\end{array} \right.\)
`c, 2x(x-2)-(2-x)=0`
`⇔ 2x(x-2)+(x-2)=0`
`⇔ (2x+1)(x-2)=0`
`⇔` \(\left[ \begin{array}{l}2x+1=0\\x-2=0\end{array} \right.\) `⇔` \(\left[ \begin{array}{l}x=\dfrac{-1}{2}\\x=2\end{array} \right.\)
`d, (x-3) +3-x=0`
`⇔x-3 + 3-x=0`
`⇔0=0`
`⇒x∈R`
`g, 5x(x-2000) – x+2000=0`
`⇔5x(x-2000)-(x-2000)=0`
`⇔(5x-1)(x-2000)=0`
`⇔` \(\left[ \begin{array}{l}5x-1=0\\x-2000=0\end{array} \right.\) `⇔` \(\left[ \begin{array}{l}x=\dfrac{1}{5}\\x=2000\end{array} \right.\)
`h, x – 4x = 0`
`⇔ -3x = 0`
`⇔ x = 0`
`k, (1-x) – 1+x=0`
`⇔1-x-1+x=0`
`⇔0=0`
`⇔x∈R`
`m, x +6x = 0`
`⇔ 7x =0`
`⇔x=0`